Gio n Hnh hc 8Nm hc 2011-2012 1 NS:06/02/2012 NG:09/02/2012(8b) 10/02/2012(8a) Chng III. TAM GIC NG DNG Tit 37NH L TA-LT TRONG TAM GIC I.MC TIU 1.Kin thc: - Tnh c t ss ca hai on thng theo cng mt dn v o.Bit c t s ca hai on thng khng ph thuc vo cch chn n v o. 2.K nng: - Da vo t s ca hai on thng v t l thc ch ra c cc on thng t l trong bi ton n gin. - Hiu nh l Ta-lt v tnh cht ng phn gic ca tam gic. - Vn dng c nh l ta-lt chng minh hai ng thng song song. 3.Thi : - Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.Gio vin: Thc, eke, bng ph 2.Hc sinh: Thc, eke III.PHNG PHP Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1:Khi ng(Gii thiu v to tnh hung).5 *Mc tiu: Gii thiu s lc v ni dung ca chng v to tnh hung vo bi mi. * dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng cua HS -GV:giithiunidungca chngvtotnhhungvobi nh sgk. HS ch nghe ging Hot ng 2:T s ca hai on thng v on thng t l20 *Mc tiu: Hiu th no l t s ca hai on thng. * dng: Thc, bng ph *Cch tin hnh: GV: C lp lm ?1 D CB A 1.T s ca hai on thng. HS : Cho AB = 3cm; CD = 5cm35ABCD =Cho EF = 4dm; MN = 7dm Gio n Hnh hc 8Nm hc 2011-2012 2 + Cho bit CDAB v MNEF? + Khi ABCD gi l t s ca hai on thng AB v CD K hiu: ABCD +NuAB=300cm;CD=400cm th t s ca AB v CD l g? +Tsca2ngthngcph thuc cch chn n v khng? -GV:Clplm?2vrtranh ngha on thng t l -GV cht li. 47EFMN =HS : 53CDAB = ; 74MNEF =HS : 34ABCD =(1) HS : khng. V nu AB = 3; CD = 4 Th 34ABCD =(2) T (1) v (2) => t s khng ph thuc n v 2.on thng t l D' C'B' A'D CB A - Hs : ?2 ' '' 'AB A BCD C D=KhitaniABv CD t l vi AB v CD. Hot ng 3:Tm hiu nh l ta-lt15 * Mc tiu: Hiu nh l ta-lt v vn dng vo gii bi tp * dng: Thc. * Cch tin hnh:

a C' B'CBA - GV: C lp lm ?3 Trnychltrnghpcth, tng qut ta c nh l sau: ...... - c ni dung nh l Talt? +Ngoicconthngtltrnta cn suy ra t s no? + Cht li ni dung ca nh l Talt. 3. nh l ta-lt trong tam gic - HS : Trnh by ti ch Gio n Hnh hc 8Nm hc 2011-2012 3 nh l ny tha nhn khng chng minh. GV:pdngnhlTaltccem lm v d sau Tmx trong hnh v (bng ph) MN // EFx 24 6,5N MF ED + Nhn xt bi lm ca bn? + Cha v cht li ni dung ca nh l Talt GV: cc nhm lm ?4 + Yu cu HS a ra kt qu, sau cha theo nhm - nh ngha t s ca 2 on thng, onthngtl?Chovdminh ho? -VitnidungnhlTaltbng hnh v? - GV pht biu li ni dung nh l HS:Nu1ngthngsong song vi 1 cnh ca tam gic v ct 2cnh cnli th nnhra trn2cnhnhngon thng t lHS : ' ' ' 'AB ACA B A C=' ';' ' ' 'BB CC AB ACAB AC BB CC= =HS ghi bi HS : V MN//EF nn theo nh l Talt c 6, 5 422.6, 53, 254DMX DNME NF xx= == = HS nhn xt HS hot ng nhm HS a ra kt qu nhm A 3x DE 5 10 BC Gio n Hnh hc 8Nm hc 2011-2012 4 HS tr li , ln bng vit .

HS ch nghe V.HNG DN V NH5 Hc nh ngha, nh l theo SGKBi tp v nh: 4,5/ tr58 * HD bi 5:a)TheogtMN//BCtac: AM AN AM ANhayMB NC MB AC AN= = Thays vo tm c x . NS:07/02/2012 NG:10/02/2012(8b) A 4 5 M N xBC BC Gio n Hnh hc 8Nm hc 2011-2012 5 11/02 (8a)Tit 38 NH L O V H QU CA NH L TA-LTI.MC TIU 1.Kin thc: - Hiu c cch chng minh h qu ca nh l o l da vo nh l ta-lt v tnh cht ca hnh bnh hnh ch ra cc on thng l cc cnh ca tam gic. 2.K nng: -Vcngphngic,odcdicconthngmng phn gic nh ra trn cnh din v di cc cnh bn, t tnh c t s di cc cnh bn tng ng vi cc on thng thuc cnh y. - Vn dng c nh l o ca nh l ta-lt gii bi tp. 3.Thi : - Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.Gio vin: Thc, eke, bng ph 2.Hc sinh: Thc, eke III.PHNG PHP Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1:Khi ng(Kim tra v to tnh hung vo bi). 5 * Mc tiu: Ti hin nh l ta-lt trong tam gic v to tnh hung vo bi mi. * dng: Thc. - Cch tin hnh: Hot ng ca GVHot ng cua HS 1. Pht biu nh l Talt V hnh minh ho? 2. Cha bi tp 5b/59 SGK HS 1: Pht biu nh l HS2: MN//BC=> AM ANAB NC=;AM AN BM NCAB AC AB AC= =HS 2: Ta cQF =DF-DQ=24-9 =15 V PQ//EF =>DP DQPE QF==> 96, 310, 5 15xx = => =Vy DP = 6,3 - HS nhn xt. D x9 24 PQ 10,5 E FF E F Gio n Hnh hc 8Nm hc 2011-2012 6 - GV gi HS nhn xt v cho im Hot ng 2:Tm hiu v nh l o20 * Mc tiu: Pht biu c nh l o. * dng: Thc, Bng ph * Cch tin hnh: GV: C lp lm ?1 bng ph? + So snh cc t s ' ABAB v ' ACAC +VngthngaiquaBv songsongviBC,ngthnga ct AC ti C? + Tnh AC? +NhnxtvCvCBCv BC? +T?1tacnhlsau.c SGK? GV: Nghin cu ?2 bng ph? Hnh 914710 65 3FE DC BA + Trong hnh v c bao nhiu cpng thng song song? +TgicBDEFlhnhg?V sao? + So snh cc t s; ;AD AE DEAB AC BC

v nhn xt? 1. nh l oHS v hnh vo v ghiAB = 6cm AC = 9cm AB = 2cmAC = 3cmHS : ' 2 16 3ABAB = =' 3 19 3ACAC = ==>' ABAB=' ACAC HSV hnh vo v ghi AC =3cm C C v BC BC HScnhlocanhl Talt?2 HS: c bi Hai cp ng thng song song TgicBDEFlhnhbnhhnh. V c 2 cp cnh i song song A C"a B' C' B C B C Gio n Hnh hc 8Nm hc 2011-2012 7 HS :Cctstrnbngnhau. AD AE DEAB AC BC= =Nhn xt: cc cp cnh ca 2 tam gic ADE v ABC t l Hot ng 3:H qu ca nh l ta- let15 * Mc tiu: pht biu c h qu ca nh l ta-lt. * dng: Thc, bng ph * Cch tin hnh: DC' B'C BA GV: c h qu ca nh l Talt? + v hnh ghi GT - KL ca h qu + Cho bit hng chng minh + Yu cu HS t chng minh vo v GV:arahnhv11/61bng ph YucuHSxtxemhqucn ng trong H11 khng ? - a ra ch * Cng c: Lm ?3/62 a) Do DE//BC ta c : 2. H qu ca nh l Talt HSc h quHSV hnh vo v ghi............ GT AABC; BC//BC KL ' ' ' ' AB AC B CAB AC BC= = Chng minh SGK/61 HS:pdngnhlTalti vi +) BC//BC + CD//AB (t k) HS trnh by vo vHS tr li : ngHShotngnhm,idin nhm ln trnh by.*Ch : SGK/61 Gio n Hnh hc 8Nm hc 2011-2012 8 AD DE 2 x 2.6,5xAB BC 5 6,5 5= = = =... b) Do MN//PQ ta c :0N MN 2 3 2.5,2x0P QP x 5,2 3= = = =... Ccnhmnhnxtvsa cha. V.HNG DN V NH5 - Hc nh l o v h qu ca nh l Talt . - BTVN: 7,9/ tr63 * Hng dn bi 7a: p dng h qu nh l Ta-lt ta c EFMNDEDM= , t thay s vo tnhx = EF

NS:13/02/2012 NG:16/02/2012(8b) 17/02 (8a) Tit 39LUYN TPI.MC TIU 1.Kin thc: - Ti hin li nh l o v h qu ca nh l ta-lt. 2.K nng: -Vcngphngic,odcdicconthngmng phn gic nh ra trn cnh din v di cc cnh bn, t tnh c t s di cc cnh bn tng ng vi cc on thng thuc cnh y. Gio n Hnh hc 8Nm hc 2011-2012 9 - Vn dng c nh l o ca nh l ta-lt v h qu ca nh l vo lm bi tp.3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.Gio vin: Thc, eke, bng ph 2.Hc sinh:Thc, eke III.PHNG PHP Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khi ng(Kim tra bi c).5 *Mc tiu: Ti hin nh l o v h qu ca nh l ta-lt trong tam gic* dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng cua HS Kim tra bi c- GV: a ra hnh v - Gi HS ln bng trnh by + Da vo s liu ghi trn hnh v c thrtranhnxtgvhaion thng DE v BC + Tnh DE nu BC = 6,4 cm? *) t vn : Nh sch gio khoa A 2,5 3 DE 1,51,8 B6,4C Gii: 1, 5 32, 5 5BDAD = =; 1,8 33 5ECEA = =BD ECAD EA= DE//BC Hot ng 2Cha bi tp v chng minh v tnh ton15 *Mc tiu:: lm c cc bi tp chng minh n gin. * dng: Thc. *Cch tin hnh: Bi 10/63 (13 pht) *HS lm vic theo nhm Bi 10/63 CHBH'C'B'Ad Gio n Hnh hc 8Nm hc 2011-2012 10 - HS cc nhm trao i - i din cc nhm tr li -Sosnhktqutnhtoncacc nhm *pdngTa-letvodngon thng

Gvgiccnhmnhnxtvcho im Gii: a)- Cho d // BC ; AH l ng cao Ta c: ' AHAH= ' ABAB (1) M ' ABAB= ' ' B CBC (2) T (1) v (2)' AHAH= ' ' B CBC b) Nu AH' = 13AH thSA AB'C'= 1 1 1 12 3 3 9AH BC| || | = | |\ .\ . SAABC

=7,5 cm2 -HS nhn xt Hot ng 3Chabitpvnhlovhquca nh l 20 *Mc tiu: Ti hin nh l o v h qu ca nh l ta-lt trong tam gic* dng:Thc. *Cch tin hnh: Cha bi 14 (10 pht) a) Dng on thng c di x sao cho: xm= 2 Gii - V^xoy-LytrnoxcconthngOA= OB = 1 (/v) - Trn oy t on OM = m -NiAMv kBN//AM tacMN = OMON = 2 m Bi 14 x B 1 A 1 0m my MN

Bx Gio n Hnh hc 8Nm hc 2011-2012 11 b) 23xn =- V xoy- Trn oy t on ON = n - Trn ox t on OA = 2 OB = 1 - Ni BN v k AM// BN ta cx = OM =23n *Cng c, luyn tp (13 pht) - GV: Cho HS lm bi tp 12 -GV:Hngdncchoc AB A

0 M Ny Bi 12 (sgk-64) V.HNG DN V NH5 - Lm cc bi tp 11,13 - Hng dn bi 13 Xem hnh v 19 s dng c nh l Talet hay h qu y c yu t song song ? A, K ,C c thng hng khng? - Si dy EF dng lm g? * Bi 11: Tng t bi 10. Gio n Hnh hc 8Nm hc 2011-2012 12 NS:14/02/2012 NG:17/02/2012 (8b) 18/02/2012 (8a) Tit 40 3.TNH CHT NG PHN GIC CA TAM GIC I.MC TIU 1.Kin thc: - Bit v ng phn gic, o c di cc on thng m ng phn gic nh ra trn cnh i din v di cc cnh bn v ni dung nh l. 2.K nng: - Tnh c t s di cc cnh bn tng ng vi cc on thng thuc cnhyvbittnhtondicacconthngvchngminhhnhhc da v tnh cht ca ng phn gic.3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.Gio vin: Thc, eke, bng ph 2.Hc sinh: Thc, eke III.PHNG PHP Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khi ng(Gii thiu v to tnh hungvo bi). 5 *Mctiu:Tihinlingphngiccuutamgicvtotnh hung vo bi mi. * dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng ca HS a- Kim tra bi c: Thnolngphngictrong tam gic? *) t vn :- GV: Gii thiu bi: Bi hm nay ta s cng nhau nghin cungphngiccatamgic ctnhchtgnavncp dng ntn vo trong thc t? - HS tr li cu hi ca Gv - HS ch lng nghe. Hot ng 2Tm hiu v nh l25 *Mc tiu: Vn dng c nh l vo gii bi tp. * dng: Thc, com pa Gio n Hnh hc 8Nm hc 2011-2012 13 *Cch tin hnh: - GV: Cho HS lm bi tp?1 CDBA36 -GV:ChoHSphtbiuiunhn xt trn ? chnh l nh l - Yu cu HS pht biu nh l v ghi gt v kl ca nh l ECDBA -GV:davokinthchcv on thng t l mun chng minh t s trn ta phi da vo yu t no? ( T nh l no) -Theoemtacthtorang thng//bngcchno?Vyta chng minh nh th no? - HS trnh by cch chng minh - Gi HS nhn xt 1:nh l: ?1+ V tam gic ABC: AB = 3 cm ; AC = 6 cm; ^A= 1000 + Dng ng phn gic AD +oDB;DCrisosnh ABAC v DBDC

Tac: ABAC=3 16 2=; 2, 55DBDC =2, 5 15 2= ABAC= DBDC nh l: (sgk/65) GTABC:ADltiaphn gic ca - BAC( D e BC ) KLABAC= DBDC Chng minh Qua B k Bx // AC ct AD ti E: Ta c:^ ^CAE BAE = (gt) v BE // AC nn ^ ^CAE AEB =(slt) ^ ^AEB BAE =doAABEcnti BBE = AB (1) p dng h qu ca nh l TaletvoADAC ta c:DBDC= BEAC (2) T (1) v (2) ta c ABAC= DBDC Nhn xt Hot ng 3Tm hiu ch 8 *Mc tiu: Bit trng hp nh l cn ng cho c tia phn gic ca gc ngoi ca tam gic. * dng: Thc, com pa. *Cch tin hnh: -GV:aratrnghptia phn gic gc ngoi ca tam gic

' D BDC= ABAC ( AB=AC ) 2) Ch :

Gio n Hnh hc 8Nm hc 2011-2012 14 - GV: V sao AB=AC *nhlvnngvitia phn gic gc ngoi ca tam gic HS lm ?2 ; ?3A 4,57,5 BxDyC -HSlmvictheonhm nh - i din cc nhm tr li x E3H F 5 8,5 E'D'BCA *nhlvnngvitiaphngicgc ngoi ca tam gic ' D BDC= ABAC ( AB=AC ) ? 2 Do AD l phn gic ca ^BAC nn: 3, 5 77, 5 15x ABy AC= = =+ Nu y = 5 thx = 5.7 : 15 = 73 ?3Do DH l phn gic ca ^EDF nn 5 38, 5 3DE EHEF HF x= = =x-3=(3.8,5):5 = 8,1 Hot ng 4Cng c v luyn tp5 *Mc tiu: Vn dng kin thc mi hc vo lm bi tp. * dng: Thc. *Cch tin hnh: *Cng c,luyn tp: Bi tp 17 Gio n Hnh hc 8Nm hc 2011-2012 15 - GV yu cu HS lm bi tp 17 MCBEDA -GVgiHSkhcnhnxtvGV cha li MCBEDA Gii: Do tnh cht phn gic: ;BM BD MC CEMA AD MA EA= =mBM=MC (gt) BD CEDA AE= DE // BC ( nh l o ca Ta-lt HS nhn xt. V.HNG DN V NH2 - Lm cc bi tp: 15; 19; 20 sgk-67 v 68

NS:20/02/2012 NG:23/02/2012(8b) 24/02/2012(8a) Gio n Hnh hc 8Nm hc 2011-2012 16 Tit 41LUYN TPI.MC TIU 1.Kin thc: - Ti hin li nh l v tnh cht ng phn gic ca tam gic 2.K nng: -Vcngphngic,odcdicconthngmng phn gic nh ra trn cnh din v di cc cnh bn, t tnh c t s di cc cnh bn tng ng vi cc on thng thuc cnh y. 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.Gio vin: Thc, eke, bng ph 2.Hc sinh:Thc, eke III.PHNG PHP Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khi ng(Kim tra bi c).5 *Mctiu:Tihinnhlvtnhchtngphngiccatam gic * dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng ca HS Kim tra bi c Pht biu nh l ng phn gic ca tam gic? - GV: Dng bng ph 1) Cho hnh v: - Cc nhm HS lm vic

ADltiaphngicca- A GT AB = 3 cm; AC = 5 cm; BC = 6 cm KLBD = ? ;DC = ? - Cc nhm trng bo co HS pht biu nh l.

A BDC Gii: DoADlphngicca ^Annta c: Gio n Hnh hc 8Nm hc 2011-2012 17 - GV gi HS khc nhn xt 3 35 8BD AB BD ABDC AC BD DC AB AC= = = =+ + 36 8BD = BD = 2,25 DC =3,75cm Nhn xt Hot ng 2Bi tp v chng minh 20 *Mc tiu: Bit chng minh cc t s bng nhau theo hnh v. * dng: Thc, Bng ph *Cch tin hnh: 2) Cha bi 1 (sgk-68) -GVchoHSvhnhvChng minh: AE BFDE FC= ; AE BFAD BC= - Gi HS nhn xt v GV cha li Bi 19 (sgk-68) A B O a

E F DC Gii a) Gi O l giao im ca EF vi BD l I ta c: AE BI BFDE ID FC= = (1) -Sdngtnhchttlthcta c: (1)AE BFAE ED BF FC=+ + AE BFAD BC= Nhn xt Hot ng 3Bi tp v chng minh hai cnh bng nhau18 *Mc tiu: Bit chng minh cc t s bng nhau theo hnh v. * dng: Thc, Bng ph *Cch tin hnh: Gio n Hnh hc 8Nm hc 2011-2012 18 Bi tp 20 (sgk- 68) -YucuHScvsuyngh cch gii. -Nungthngaiquagiao imOcahaingchoACv BD.-Nhnxtgv2onthngOE, FO. -YucuHStrlitheocuhi hng dn ca GV v ln bng thc hin: Gi HS nhn xt? Bi 20 (sgk-68)HS c bi A B O a

E F DC Gii: Ta c: AE BFAD BC=v AE EOAD CD= ; FO BFCD BC=-pdnghquvoAADCv ABDCEO = FO Nhn xt V.HNG DN V NH2 - Lm bi 22/ sgk - Hng dn: T 6 gc bng nhau, c th lp ra thm nhng cp gc bng nhau no? C th p dng nh l ng phn gic ca tam gic - Chun b bi khi nim hai tam gic ng dng NS:21/02/2012 NG:24/02/2012(8b) 25/02/2012(8a)

Gio n Hnh hc 8Nm hc 2011-2012 19 Tit 42 4.KHI NIM HAI TAM GIC NG DNG I.MC TIU 1.Kin thc: -Lycvdvhaitamgicngdng,bittsngdngvcc tnh cht ca hai tam gic ng dng: + C kh nim v nhng hnh ng dng, + Bit hai tam gic gi l ng dng vi nhau nu cc gc bng nhau v cc cnh tng ng t l. 2.K nng: - Bc u lm quen v hai tam gic ng dng v cch v hnh tam gic ng dng. -Vndnghqu canh lTalettrongchngtrongchngminhhnh hc 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke III.PHNG PHP Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khing(Kimtravtotnhhungvo bi). 5 *Mc tiu:Ti hin li nh l talt v to tnh hung vo bi mi. * dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng cua HS -GVPhtbiuhqucanhl Talet? *) t vn : Nh sch gio khoa - HS pht biu ni dung nh l - HS ch lng nghe. Hot ng 2 Quan st nhn dng hnh c quan h c bit v tm khi nim mi 15 *Mctiu:Hnhthnhnhngha,tnhchtcahaitamgicng dng. * dng: Thc, Bng ph. *Cch tin hnh: - GV: Cho HS quan st hnh 28? Cho kinnhnxtvcccphnhv 1.Tam gic ng dng: Gio n Hnh hc 8Nm hc 2011-2012 20 ? -GV:Cchnhchnhdng ging nhau nhng c th kch thc khcnhau,lcccphnhng dng. -GV:ChoHSlmbitp?1 -GV: Em c nhn xt g rt ra t ?1 -GV:TamgicABCvtamgic A'B'C' l 2 tam gic ng dng. - HS pht biu nh ngha. AABC #AA'B'C' ' ' ' ' ' 'A B AC B CAB AC BC= = ^ ^ ^^ ^ ^' ' '; ; A A B B C C = = =-GV:ChoHSlmbitp? 2theo nhm. -Ccnhmtrlixonglmbitp ?2- Nhm trng trnh by. +Haitamgicbngnhaucth xemchngngdngkhng?Nu c th t s ng dng l bao nhiu? +AABCcngdngvichnhn khng, v sao? +NuAABC#AA'B'C'thAA'B'C'# AABC?Vsao?AABC#AA'B'C'c tskthAA'B'C'#AABClts no? - HS pht biu tnh cht. a/ nh ngha ?1AA' 4 522,5 B 6 C B' 3 C' ' '2 14 2A BAB = =; ' '2, 5 15 2ACAC = =' '3 16 2B CBC = = ; ^ ^ ^^ ^ ^' ' '; ; A A B B C C = = = Tnh cht. 1/Mitamgicngdngvi chnh n. 2/A ABC#A A'B'C'thA A'B'C'# AABC 3/AABC #AA'B'C' vAA'B'C' #A A''B''C'' thAABC #AA''B''C''. Hot ng 3Hnh thnh nh l15 *Mc tiu: Hnh thnh nh l v m rng thm phn ch . * dng: Thc, bng ph *Cch tin hnh: -GV:ChoHSlmbitp?3theo nhm. - Cc nhm trao i tho lun bi tp ?3. - C i din ln bng - GV: Cht li Thnh nh l2. nh l (SGK/71). A MN a Gio n Hnh hc 8Nm hc 2011-2012 21 -GV:ChoHSphtbiuthnhli nhlvaraphngphp chng minh ng, gn nht. - HS ghi nhanh phng php chng minh. - HS nu nhn xt ; ch . B C GT AABC c MN//BC

KL AAMN #AABC Chng minh: AABC & MN // BC (gt) A AMN#A ABCc^ ^ ^ ^; AMB ABC ANM ACB = =(gcng v) ^A l gc chung TheohqucanhlTalet AAMNvAABCc3cpcnh tngngtl AM AN MNAB AC BC= = .VyA AMN# AABC * Ch : nh l cn trong trng hp t a ct phn ko di 2 cnh catamgicvsongsongvi cnh cn li. Hot ng 5Cng c v luyn tp8 *Mc tiu: Cng c li kin thc mi hc v vn dng vo lm cc bi tp. * dng: Thc. *Cch tin hnh: -HS tr li bi tp 23 SGK/71 -HS lm bi tp sau: AABC #AA'B'C'theo t s k1 AA'B'C'#A A''B''C'' theo t s k2 ThAABC#A A''B''C''theotsno ? V sao? Bi tp 23 SGK/71 +Haitamgicbngnhauth ng dng vi nhau ng +Haitamgicngdngvi nhauthbngnhau(Sai)Vch ng khi t s ng dng l 1. Gii:1akb =; 2bkc = 1 2ak kc =AABC#A A''B''C'' theo t s k1.k2 V.HNG DN V NH2 - Lm cc bi tp 25, 26 (SGK) - Ch s tam gic dng c, s nghim. Gio n Hnh hc 8Nm hc 2011-2012 22 NS:27/02/2012 NG:01/03/2012 (8b) 02/03/2012 (8a) Tit 43LUYN TP I.MC TIU 1.Kin thc: - Ti hin li khi nim v hai tam gic ng dng v nh l. 2.K nng: -Cngclicch vhaihnh tamgicngdngvcc kinthc ln quan. - Vn dng h qu ca nh l Talet trong chng trong chng minh hnh hc 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. Gio n Hnh hc 8Nm hc 2011-2012 23 II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke III.PHNG PHP Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khing(Kimtravtotnhhungvo bi). 5 *Mc tiu: Ti hin li khi nim v nh l. * dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng cua HS -GVemhyphtbiukhinimhai tam gic ng dng v nh l? - HS pht biu ni dung. Hot ng 2Bi tp chng minh20 *Mc tiu: Vn dng c kin thc hc vo gii bi tp * dng: Thc. *Cch tin hnh: -GV:NghincuBT26/27trn bng ph -YucuHShotngtheonhm, sau a ra kt qua) cch dngTrn AB ly AM =2/3 AB T M k MN//BC (NeAC) Dng AABC = AAMN 1. bi tp 26/72 HS c biHot ng theo nhma ra kt qu nhm

b) Chng minh V MN//BC =>AAMN # AABC VAAMN = AABC => AABC #AABC(theo k =1)HS : Nhn xt A A' MN B' C BC B C Gio n Hnh hc 8Nm hc 2011-2012 24 Hot ng 3Bi tp tnh ton15 *Mc tiu: Vn dng c kin thc hc vo gii bi ton. * dng: Thc, bng ph *Cch tin hnh: GV: a bi ln bng ph +NugichuviAABCl2Pv chu vi AABC l 2P th tnh t schu vi 2 tam gic trn? Tnh 2P v 2P Lp t s: 22 'PP HS : Trnh by ....... + Gi HS trnh by v cha + Bit 2P - 2P = 40dm HytnhchuviAABC?Vchuvi AABC? + Yu cu trnh by v cha 2. bi tp 28/72 HS : Theo di bi HS:hotngtheonhm,a ra kqu nhm a) 2P = AB + BC +CA 2P = AB + BC +CA ' ' ' ' ' ' ' ' ' ' ' ' 2 32 ' 5+ += = = = =+ +A B B C C A A B B C A C PAB BC AC AB BC AC P b) C2 32 ' 5PP = => 2 ' 3 2 ' 32 ' 60( )2 2 ' 5 3 40 2= => = => = P PP dmP PV 2P = 60+40 = 100 dm V.HNG DN V NH5 - Pht biu nh ngha, tnh cht v 2 tam gic ng dng? - BTVN: 27,28 sbt- Xem li cc bi tp cha- c trc bi 6 NS:28/02/2012 NG:02/03/2012 (8b) 03/03 (8a) Tit 44 5.TRNG HP NG DNG TH NHT Gio n Hnh hc 8Nm hc 2011-2012 25 I.MC TIU 1.Kin thc: - Bit t s cc cnh tng ng gi l t s ng dng v bit c iu kin hai tam gic ng dng theo trng hp thc nht. 2.K nng: -Davotnhchthaingthngsongsongvhqucanhltalet chng minh c: Nu mt ng thng ct hai cnh ca mt tamgic v song song vi cnh cn li th n to thnh mt tam gic mi ng dng vi tam gic cho. 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khing(Kimtravtotnhhungvo bi). 5 *Mc tiu: Ti hin li khi nim v hai tam gic ng dng * dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng cua HS -Hyphtbiunhlvhaitam gic ng dng? - HS lm bi tp ?1/sgk/73 ( HS di lp lm ra phiu hc tp) - GV: Dng bng ph a ra bi tp ?1 * HS:AN = 12AC = 3 cm AM = 12AB = 2 cm - M, N nm gia AC, AB theo ( gt) MN = 2BC= 4 cm ( T/c ng trung bnhcutamgic)vMN//BC.Vy AAMN #AABC&AAMN =AA'B'C' *) t vn : Nh sch gio khoa A 23 MN 4 B 8C A' 23 B' C' 4 Hot ng 2Hnh thnh nh l.20 Gio n Hnh hc 8Nm hc 2011-2012 26 *Mc tiu: Hnh thnh nh l v trng hp ng dng th nht. * dng: Thc, bng ph. *Cch tin hnh: 1)nhl:(4pht)-GV:Quanhn xttrnemhyphtbiuthnhli nh l? AABC&AA'B'C'GT' ' ' ' ' ' A B A C B CAB AC BC= = (1) KL AA'B'C' #AABC

Chng minh nh l - GV: Cho HS lm vic theo nhm - GV: dava bi tp c th trn chngminhnhltacnthchin theo qui trnh no? 1) nh l:

A MN

B C A'

B' C' +TrncnhABtAM=A'B' (2) +TimMvMN//BC(N eAC) XtAAMN ,AABC&AA'B'C' c: AAMN #AABC( v MN // BC) do : AM AN MNAB AC BC= =(3) T (1)(2)(3) ta c: ' ' A C ANAC AC= A'C' = AN (4) ' ' B C MNBC BC= B'C' = MN (5) T(2)(4)(5) A AMN=A A'B'C'(c.c.c) VAAMN #AABC nn AA'B'C' #AABC Hot ng 3p dng15 *Mc tiu: Vn dng c nh l vo gii bi tp* dng: Thc Gio n Hnh hc 8Nm hc 2011-2012 27 *Cch tin hnh: 2) p dng: - GV: cho HS lm bi tp ?2/74 - HS suy ngh tr li. -GV:Khichotamgicbitdi3 cnh mun bit cc tam gic c ng dngvinhau khngtalmnh th no? 2) p dng: A 46 B C 8D 32 E4 F 6 HK 54 * Ta c: 2 3 4( )4 6 8DF DE EFdoAB AC BC= = = = ADEF #AACB - Theo Pi Ta Go c: AABCvung A c: BC=2 236 64 100 AB AC + = + = =10 AA'B'C' vung A' c: A'C'=2 215 9 =12;3' ' ' ' ' ' 2AB AC BCA B A C B C= = = AABC #AA'B'C' Gio n Hnh hc 8Nm hc 2011-2012 28 Hot ng 4Cng c5 *Mc tiu: Cng c li kin thc mi hc. * dng: Thc. *Cch tin hnh: a) GV: Dng bng ph AABCvungAcAB=6cm; AC = 8 cm vAA'B'C' vung A' c A'B' = 9 cm ,B'C' = 15 cm. HaiAABC&AA'B'C' c ng dng vi nhau khng? V sao? GV: ( gi ) Ta c 2 tam gic vung bitdihaicnhcatamgic vung ta suy ra iu g? - GV: kt lunVyAA'B'C' #AABCb) GV: Cho HS lm bi 29/74 sgk -HSlmbitptheosgi ca GV -HSlmBi29/74sgk: AABC& AA'B'C' c 3' ' ' ' ' ' 2AB AC BCA B A C B C= = =v( 6 9 124 6 8= = ) Ta c:27 3' ' ' ' ' ' ' ' 18 2AB AC BC ABA B A C B C A B+ += = =+ + V.HNG DN V NH2 Lm cc bi tp 30, 31 /75 sgk HD:p dng dy t s bng nhau. Gio n Hnh hc 8Nm hc 2011-2012 29 NS: 05/03/2012 NG:08/03/2012 (8b) 09/03(8a) Tit 45 6.TRNG HP NG DNG TH HAI I.MC TIU 1.Kin thc: - Vit c GT, KL ca ni dung nh l. - Hiu c cch chng minh gm ha bc chnh: Dng tam gic AMN ngdng vi tam gic ABC - v AAMN = AABC). - Vn dng c nh l nhn bit cc cp tam gic ng dng trong cc bi tp tnh di cc cnh v cc bi tp chng minh. 2.K nng: -Rn k nng vn dng nh l vo gii bi tp, k nng v hnh . 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khing(Kimtravtotnhhungvo bi). 5 *Mc tiu: Ti hin li nh l v trng hp ng dng th nht v TG, KL ca ni dung nh l. * dng: Thc. *Cch tin hnh: Gio n Hnh hc 8Nm hc 2011-2012 30 Hot ng ca GVHot ng cua HS -Phtbiunhlvtrnghp ng dng th nht ca 2 tam gic? Vhnhghi(gt),(kl)vnuhng chng minh? - t vn : Nh sch gio khoa-HSphtbiunidungnhl (SGK-73) Hot ng 2Hnh thnh nh l15 *Mc tiu: V hnh, o c v pht hin nh l. * dng: Thc. *Cch tin hnh: - o di cc on BC, FE - So snh cc t s: ; ;AB AC BCDE DF EF t rt ra nhn xt g 2 tam gic ABC & DEF? -GVchoHSccnhmlmbivo phiu hc tp. GV:Quabilmcaccbnta nhnthy.TamgicABC&Tam gicDEFc1gcbngnhau=600 v2cnhkcagctl(2cnh catamgicABCtlvi2cnh catamgicDEFv2gctobi cccpcnhbngnhau)vbn thyc2tamgicngdng =>chnhlnidungcanhl m ta s chng minh sau y. GV:Chohcsinhcnhl&ghi GT-KL ca nh l . 1. nh l: ?1. AD 43 CB 8 6 EF 4 18 2ABDE = = ; 3 16 2ACDF = = ;2, 5 15 2BCEF = ==> AB AC BCDE DF EF= ==>ABC A #DEF A . nh l : (SGK)/76.

GTABC & A'B'C' ' ' A BAB=' ' A CAC(1); =' Gio n Hnh hc 8Nm hc 2011-2012 31 AA MN B

C BC GV:Choccnhmtholun=> PPCM GV:Choidinccnhmnu ngngnphngphpchngminh ca mnh. + t ln on AB on AM=A'B' v MN//BC +CM:ABC A #A AMN; A AMN#A A'B'C' KL:A ABC #A A'B'C' PP 2: - t ln AB on AM = A' B' - t ln AB on AN= A' B' - CM:AAMN =A A'B'C' (cgc) - CM:ABC A #AAMN ( L ta let o) KL:A ABC #A A'B'C' GV: Thng nht cch chng minh . KLAA'B'C' #AABC Chng minh -Trn tia AB t AM=A'B' Qua M k MN// BC(NeAC) AAMN #AABC =>AMMB=ANAC V AM=A'B' nn ' ' A B ANAB AC= (2) T (1) v (2)AN = A' C' AAMNA A'B'C' c: AM= A'B'; - A = - A; AN = A'C' nnAAMN =A A'B'C' (cgc) ABC A #AAMN A ABC #A A'B'C' Hot ng 3p dng25 *Mc tiu: Vn dng c kin thc mi vo lm bi tp. * dng: Thc. *Cch tin hnh: - GV: CHo HS lm bi tp ?2 ti ch ( GV dng bng ph) - GV: CHo HS lm bi tp ?3 - GV gi HS ln bng v hnh. - HS di lp cng v 2) p dng: ?2 ?3 A Gio n Hnh hc 8Nm hc 2011-2012 32 + V - xAy= 500 + Trn Ax xc nh im B: AB = 5 + Trn Ayxc nh im C: AC = 7,5 + Trn Ayxc nh im E: AE = 2 + Trn Ax xc nh im D: AD = 3 - HS ng tich tr li. Cng c :- Chohnh v nhn xt cc cpAA AOC&A BOD;A AOD&A COB c ng dng khng? 2 3500 E D 5 BC 2 65 15AEAB = =3 67, 5 15ADAC = =AE ADAB AC=A AED ~A ABC (cgc) x B A. . O. CDy OA = 5 ; OC = 8 ; OB = 16 ;OD = 10 V.HNG DN V NH2 -Hng dn hc sinh hc nh. -Lm cc bi tp: 32, 33, 34 ( sgk) Gio n Hnh hc 8Nm hc 2011-2012 33 NS:06/03/2012 NG:09/03/2012 (8b) 10/03/2012 (8a) Tit 46 7.TRNG HP NG DNG TH BA I.MC TIU 1.Kin thc: - Vit c GT, KL ca ni dung nh l. -Vndngcnhlnhnbitcccptamgicngdngvinhau, bit sp xp cc nh tng ng ca hai tam gic ng dng. 2.K nng: -Lp ra cc t s thch hp t tnh ra di cc on thng trong cc hnh v phn bi tp. 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khing(Kimtravtotnhhungvo bi). 5 *Mc tiu: Ti hin li nh l v trng hp ng dng th hai v TG, KL ca ni dung nh l. * dng::Thc. *Cch tin hnh: Hot ng ca GVHot ng cua HS -Phtbiunhlvtrnghp ng dng th nht v th hai ca 2 tamgic?-Vhnhghi(gt),(kl)v nu hng chng minh? *V:Hmnaytasnghincu thmmttrnghpngdng nacahaiA mkhngcno di cc cnh ca 2A - HS ln bng - HS khc lm ra nhp Hot ng 2Hnh thnh nh l15 *Mc tiu: V hnh v chng minh c nh l. Gio n Hnh hc 8Nm hc 2011-2012 34 * dng: Thc, bng ph *Cch tin hnh: -GV:ChoHSlmbitp bng ph ChoAABC&A A'B'C c =' , - B= - B Chng minh :AA'B'C'#AABC - GV yu cu HS c bi. - GV yu cu HS v hnh , ghi GT, KL. -GV:YucuHSnucch chngminhtngtnh cchchngminhnhl1v nh l 2. - GV yu cu HS pht biu ni dung nh l. - HS nu kt qu v pht biu nh l. 1. nh l: Bi ton: ( sgk) AABC&A A'B'C GT - A- =A;- B= - B

KLAABC#A A'B'C

AMNB CA'B'C' Chng minh - t trn tia AB on AM = A'B' -QuaMkngthngMN//BC(N eAC) V MN//BCA ABC #A AMN(1) XtA AMN&A A'B'C c: = (gt) AM = A'B' ( cch dng) - AMN= - B( ng v) - B= - B(gt) - AMN= - B AABC #AA'B'C' - HS cnh l: ( SGK) Gio n Hnh hc 8Nm hc 2011-2012 35 Hot ng 3p dng23 *Mc tiu: Vn dng c nh l vo lm bi tp. * dng: Thc. *Cch tin hnh: - GV yu cu HS lm ?1( sgk-78) GV a bng ph cc hnh v v yu c HS thc hin. -GV:Chngminhrngnu2A ngdngthtshaingcao tngngcachngcngbngt s ng dng - GV: cho HS lm bi tp ?2 - HS lm vic theo nhm DCBAxy4,53 -Gv yu cu HS tr li v nhn xt. Cng c, luyn tp- Nhc li nh l - Gii bi 36/sgk 2) p dng ?1 HS tr li: - Cc cpA sau ng dng A ABC #A PMN A A'B'C' #A D'E'F' -Ccgctngngca2A ng dng v bng nhau 500

?2 A ABC #A ADB - Achung ; - ABD= - ACB AB ACAD AB= AB2 = AD.AC x = AD = 32 : 4,5 = 2 y = DC = 4,5 - 2 = 2,5 -HS nhn xt. V.HNG DN V NH2 -Hc thuc ni dung nh l. -Lm cc bi tp 37, 38, 39 / sgk. Gio n Hnh hc 8Nm hc 2011-2012 36 NS: 10/03/2011 NG:12/03/2011 (8a, b) Tit 47LUYN TP I.MC TIU 1.Kin thc: - Ti hin li cc nh l v cc trng hp ng dng ca tam gic. - Vn dng c cc nh l vo gii bi tp. 2.K nng: - Vn dng c cc trng hp ng dng ca tam gic gii ton. - Bit ng dng tam gic ng dng o gin tip cc khong cch.3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Kim tra 1515 *Mc tiu: Ti hin li khi nim v nh l v cc trng hp ng dng ca tam gic. * dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng cua HS - GV: Cho hnh v v s o nh sau: DCBAxy4,53 Hy tnh di x v y theo hnh v. - HS thc hnh lm bi kim tra. A ABC #A ADB - Achung ; - ABD= - ACB AB ACAD AB= AB2 = AD.AC x = AD = 32 : 4,5 = 2 y = DC = 4,5 - 2 = 2,5 Hot ng2Cha bi tp nh tnh12 *Mc tiu: Ti hin li khi nim v nh l v cc trng hp ng dng ca tam gic, vn dng cc nh l vo gii bi tp. * dng: Thc. Gio n Hnh hc 8Nm hc 2011-2012 37 *Cch tin hnh: GV yu cu HS lm bi tp 36 (sgk-79) V mt HS ln bng thc hin. - Gv gi HS khc nhn xt. HS thc hin: D CBAX12,528,5 A ABD vA BDCc: - A = - DBCv - ABD = - BDC AABD # ABDC=>ABBD= BDDC+ T ta c : x2= AB.DC = 356,25 =>x~ 18,9(cm) HS nhn xt. Hot ng 3Bitpvndngchngminhtamgicng dng 15 *Mc tiu: Vn dng nh l vo bi* dng: Thc. *Cch tin hnh: Bi tp 38 (SGK- 79) CEDB A23xy63,5 -Muntmcx,ytaphichng minh c 2A no # v sao ? - Vit ng t s ng dng * Gio vin cho hc sinh lm thm : V1ngthngquaCv vung gc vi AB ti H , ct DE ti K. Chng minh: CHCK= ABDE -HS cha bi tp 2) Cha bi 38 VAB= 12 DE - B= - D (soletrong) - C 1 = - C 2(i nh) AABC ng dng viAEDC (g g) Gio n Hnh hc 8Nm hc 2011-2012 38 GV gi HS nhn xt. - GV: Nhc li cc phng php tnh di cc on thng, cc cnh ca tamgicdavotamgicng dng. -Bi39tngtbi38GVara phng php chng minh. ABDE= ACEC= BCDC

Ta c : 3, 5x=36 x= 3.3, 56= 1,75 2y= 36 y =2.63= 4 V:BH//DK - B= - DCH CBCK CD=(1)v BCDC= ABDE(2) T (1) (2) pcm ! HS nhn xt. HSch lng nghe. V.HNG DN V NH3 - Lm cc bi tp 41,42, 43,44,45.- Hng dn bi:44 + Da vo tnh cht tia phn gic lp t s + Chng minh hai tam gic ng dng theo trng hp g.g NS:12/03/2011 NG:14/03/2011(8a) 15/03/2011(8b) Tit 48 CC TRNG HP NG DNG CA TAM GIC VUNG I.MC TIU 1.Kin thc: - Vit c GT, KL ca ni dung nh l, hiu c Cc trng hp ng dng ca hai tam gic vung. - Vn dng c nh l nhn bit cc cp tam gic ng dng vi nhau, bit sp xp cc nh tng ng ca hai tam gic ng dng. 2.K nng: -Vn dng c cc trng hp ng dng ca tam gic vung gii ton. Gio n Hnh hc 8Nm hc 2011-2012 39 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khing(Kimtravtotnhhungvo bi). 5 *Mctiu:Tihinlinhlvtrnghpngdngthhaivto tnh hung vo bi mi. * dng: Thc. -CTH: Hot ng ca GVHot ng cua HS - Vit dng tng qut ca cc trng hpngdngca2tamgic thng. -Chracciukincnckt lun hai tam gic vung ng dng ? - GV: Cht li phn trnh by ca HS v vo bi mi -Nu2tamgicvungcmt gcnhnbngnhauth2tam gic ng dng.-Nu2cnhgcvungcaAnytlvi2cnhgcvung caAvungkiathhaiA ng dng. Hot ng 2 pdngcctrnghpngdngcatam gic vo tam gic vung. 5 *Mctiu:Vndngccctrnghpngdngvotamgic vung. * dng: Thc, bng ph *Cch tin hnh: - GV: Hai tam gic vung ng dng vi nhau khi no? 1)pdngccTHngdng catamgicthngvotam gic vung. Hai tam gic vung c ng dng vi nhau nu: a)Tamgicvungnycmt gc nhn bng gc nhn ca tam gic vung kia. b)Tamgicvungnychai cnh gc vung t l vi hai cnh gcvungcatamgicvung Gio n Hnh hc 8Nm hc 2011-2012 40 kia. Hot ng 3 Duhiucbitnhnbithaitamgic vung ng dng 15 *Mc tiu: Bit du hiu nhn bit hai tam gic vung c bit. * dng: Thc, bng ph *Cch tin hnh: - GV: Cho HS quan st hnh 47 & ch ra cc cpA ng dng - GV: T bi ton chng minh trntacthnumttiu chunnanhnbithaitam gic vung ng dng khng ?Hyphtbiumnh? Mnhnutachngminh c n s tr thnh nh l - HS pht biu: nh l: AABC &AA'B'C', - A= - A =900 GT ' ' ' ' B C A BBC AB= ( 1) KL AABC #AA'B'C' - HSchng minh di s hng dn ca GV: - Bnh phng 2 v(1) ta c: -pdngtnhchtcadyts bng nhau ta c? - Theo nh l Pi ta go ta c? 2.Duhiucbitnhnbit2 tam gic vung ng dng: * Hnh 47:A EDF #A E'D'F' A'C' 2 = 25 - 4 = 21 AC2 = 100 - 16 = 84 2' ' 8421A CAC| | = |\ .= 4; ' ' ' '2A C A BAC AB= =AABC #AA'B'C' nh l( SGK) B B A

C

A C Chngminh:T(1)bnhphng 2 v ta c :2' ' ' '22 2BC ABBC AB=Theo t/c ca dy t s bng nhau ta c: 2' ' ' '2 ' '2 ' '22 2 2 2BC AB BC ABBC AB BC AB= = Ta li c: BC2 AB2 =AC2 Gio n Hnh hc 8Nm hc 2011-2012 41 BC2 - AB2 = AC2 ( nh l Pi ta go) Do :2' ' ' '2 ' '22 2 2BC AB ACBC AB AC= = ( 2) T (2 ) suy ra:' '' ' ' ' B C A B A CBC AB AC= =Vy AABC #AA'B'C'. Hot ng 4 T s hai ng cao, t sdin tch ca hai tam gic ng dng. 10 *Mctiu:BitTshaingcao,tsdintchcahaitamgic ng dng * dng: Thc, bng ph *Cch tin hnh: -GVyucuHScnhl2v t chng minh -GVyucuHScnhl3v t chng minh 3)Tshaingcao,tsdintchcahai tamgicng dng. * nh l 2: ( SGK) A A' BHCB'H' C' * nh l 3: ( SGK) A BHC Gio n Hnh hc 8Nm hc 2011-2012 42 V.HNG DN V NH2 - LmBT 47, 48 HD: p dng t s din tch ca hai A ng dng, T s hai ng cao tng ng. NS:13/03/2011 NG:15/03/2011(8a) 17/03/2011(8b) Tit 49LUYN TP I.MC TIU 1.Kin thc: -Tihincctrnghpngdngcatamgic vung. -Vndngcnhlnhnbitcccptam gic ng dng vi nhau, bit sp xp cc nh tng ng ca hai tam gic ng dng. 2.K nng: -Vn dng c cc trng hp ng dng ca tam gic vung gii ton. 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khi ng5 *Mc tiu: Ti hin li nh l v cc trng hp ng dng ca tam gic vung. Gio n Hnh hc 8Nm hc 2011-2012 43 * dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng cua HS GV : Nu cc du hiu nhn bit hai tam gic vung ng dng. ( Lin h vitrnghpca2tamgic thng) - HS nu theo yu cu ca HS Hot ng 2Bi tp m rng 15 -MT:Tihinlinhlvcctrnghpngdngcatamgic vung. * dng: Thc. *Cch tin hnh: Bi tp trn cho thm AB = 12,45 cm AC = 20,5 cm a) Tnh di cc on BC; AH; BH; CH. b)Quavictnhdiccon thngtrnnhnxtvcngthc nhn c - GV: Cho HS lm bi v cht li. Nhn xt : - Qua vic tnh t s # ca 2 tam gic vungtatmlicngthccanh l PITAGO v cng thc tnh ng cao ca tam gic vung a) p dng PitagoA ABC c: BC2 = 12,452 + 20,52 BC = 23,98 m b) TAng dng (CMT) 2AB BH ABBHBC AB BC= =2AC CH ACCHBC AC BC= = HB = 6,46 cm AH=10,64cm;HC=17,52 cm Hot ng 3Bi tp nhn dng v nh tnh.22 *Mc tiu: Ti hin li nh l ta-lt, pitago v tam gic vung. * dng: Thc. *Cch tin hnh: Cha bi 50 (8) -GV:HngdnHSphichra c : Bi 50 AH2 = BH.HC AH = 30 cm SAABC = 1.30.61 9152=cm2 Gio n Hnh hc 8Nm hc 2011-2012 44 +Cctianngtrongcngmtthi im xem nh cc tia song song. + V hnh minh ha cho thanh st v ng khi + Nhn bit c 2 Ang dng . - HS ln bng trnh by -dilpccnhmcngtho lun B A D F C - Ta c: AABC # ADEF (g.g) . AB AC AC DEABDE DF DF= =Vi AC = 36,9 m DF = 1,62 m DE = 2,1 m AB = 47,83 m V.HNG DN V NH3 - Lm tip bi tp cn li - Chun b gi sau: + Thc vung +Thc cun (Thc mt cun) + Gic k- LmBT 47, 48 NS:13/03/2011 NG:15/03/2011(8a) 17/03/2011(8b) E Gio n Hnh hc 8Nm hc 2011-2012 45 Tit50NGDNGTHCTCATAMGIC NG DNG I.MC TIU 1.Kin thc: - Ti hin li cc trng hp ng dng ca tam gic. 2.K nng: - Vn dng c cc trng hp ng dng ca tam gic gii ton. - Bit ng dng tam gic ng dng o gin tip cc khong cch. 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khing(Kimtravtotnhhungvo bi). 5 *Mc tiu: Ti hin li cc nh l v trng hp ng dng ca tam gic v to tnh hung vo bi mi. * dng: Thc, Gic k, thc ngm *Cch tin hnh: Hot ng ca GVHot ng cua HS - GV: o chiu cao ca 1 cy, hay 1 ct c m khng o trc tip vy ta lm th no? - GV: HS nhn xt Cch o + Cm 1 cc mt t +odibngcacyv di bng ca cc. +ochiucaocacc(Phn nm trn mt t) T s dng t s ng dng. Ta c chiu cao ca cy. Hot ng 2Tm cch o gin tip chiu cao ca vt 15 *Mc tiu: Bit cch o gin tip chiu cao ca vt. * dng: Thc, Gic k, thc ngm *Cch tin hnh: 1) o gin tip chiu cao ca vt -GV:ChoHShotngtheotng nhmtraoivtmcchochiu cao ca cy v GV nu cch lm. 1)ogintipchiucaoca vt + Bc 1: Gio n Hnh hc 8Nm hc 2011-2012 46 C' C BA A' - HS hot ng theo nhm -Ccnhmbocovrtracch lmng nht. - VD: oAB = 1,5, A'B = 4,5 ; AC = 2 Th cy cao my m? - HS Thay s tnh chiu cao H2:Tmcchokhongcchca 2imtrnmtt,trongc1 im khng th ti c. - t thc ngm ti v tr A sao chothcvunggcvimt t,hngthcngmiqua nh ca cy. -XcnhgiaoimBca ngthngAA'ving thng CC' (Dng dy). Bc 2: - o khong cch BA, AC & BA' DoA ABC#A A'B'C' '' '.A BAC ACAB = - Cy cao l '' '4, 5. .2 61, 5A BAC AC mAB= = = Hot ng 3 okhongcchca2imtrnmtt trong c 1 im khng th ti c 22 *Mc tiu: Bit o khong cch gia hai a im trong c mt im khng n c. * dng: Thc, Gic k, thc ngm *Cch tin hnh: 2.okhongcchca2imtrn mtttrongc1imkhng th ti c - GV: Cho HS xem H55 Tnh khong cch AB ? 2.okhongcchca2im trn mt t trong c 1 im khng th ti c B1: o c - Chn ch t bng phng; vch 1onthngcdituchn (BC = a) Gio n Hnh hc 8Nm hc 2011-2012 47 A BaC - HS suy ngh, tho lun trong nhm tmcchockhongcchni trn -HSSuynghphtbiutheotng nhm *Cng c -GVcho2HSlnbngnlicch sdnggicko2gcto thnh trn mt t. -GV:ChoHSnlicchsdng gic k ng o gc theo phng thng ng. -Dnggickogctrnmt t o cc gc - ABC = o , - ACB = |B2: Tnh ton v tr li: V trn giyAA'B'C' vi B'C' = a'

- B = o, - C = | c ngayAABC #AA'B'C' '' ' ' ' ' ''. AB BC A B BCABA B BC BC = =- p dng+ Nu a = 7,5 m + a' = 15 cm A'B' = 20 cm Khongcchgia2imAB l: 750.20 100015AB = =cm = 10 m -HSlntrnhbycchogc bng gic k ngang -HStrnhbyvbiudincch o gc s dng gic k ng V.HNG DN V NH3 - Tm hiu thm cch s dng 2 loi gic k - Xem li phng php o v tnh ton khi ng dngAng dng. - Chun b gi sau: - Mi t mang 1 thc dy (Thc cun) hoc thc ch A 1m + dy thng. Gi sau thc hnh(Bt thc thng c chia mm, eke, o ). o | Gio n Hnh hc 8Nm hc 2011-2012 48 NS:17/03/2011 NG:19/03/2011(8a, b) Tit 51 THC HNH I.MC TIU 1.Kin thc: - Ti hin li cc trng hp ng dng ca tam gic. - Vn dng c cc trng hp ng dng ca tam gic thc hnh. 2.K nng: -Bitngdngtamgicngdngogintipcckhongcchtrong thc hnh. 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton v thc hnh. II. DNG DY HC 1.GV: Thc, Thc o gc, gic k. Thc ngm, thc dy, giy bt. 2.HS:Thc, eke III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khi ng2 *Mc tiu: Kim tra s chun b ca HS v kin thc v dng c.. * dng: Thc, Gic k, thc ngm *Cch tin hnh: Hot ng ca GVHot ng cua HS - GV: o chiu cao ca 1 cy, hay 1 ct c m khng o trc tip vy ta lm th no? - Kim tra s chun b ca HS -HS tr li Hot ng 2Hng dn HS thc hnh v thc hnh35 *Mc tiu: Hng dn HS thc hnh.. * dng: Thc, Gic k, thc ngm Gio n Hnh hc 8Nm hc 2011-2012 49 *Cch tin hnh: B1: - GV: Nu yu cu ca bui thc hnh +ochiucaocactcsn trng + Phn chia 4 t theo 4 gc 4 v tr khc nhau B2: -Cctnghe,xcnhvtrthc hnh ca t mnh -HScctvngvtrvtin hnh thchnh - HS lm theo hng dn ca GV -GV:nccctlmvic,o ngm cho chun. C' C B AA' - HS thc hnh o c thc t ghi s liu B1:Chnvtrtthcngm( gickng)saochothc vunggcvimtt,hng thc ngm i qua nh ct c. B2: Dng dy xc nh giao im ca' v CC' B3: o khong cch BA, AA' B4:Vcckhongcchtheo tltutheotrngiyvtnh ton tm C'A'B5: tnh chiu cao ca ct c: Khong cch: A'C' nhn vi t s ng dng ( Theo t l) Hot ng 3Cng c v luyn tp5 *Mc tiu: Cng c v nhc nh HS v gi thc hnh. * dng: Thc, Gic k, thc ngm *Cch tin hnh: Gio n Hnh hc 8Nm hc 2011-2012 50 -GV:Kimtranhgioctnh ton ca tng nhm. - GV: lm vic vi c lp. +Nhnxt ktquoc catng nhm + Thng bo kt qu ng. +nghacavicvndngkin thctonhcvoisnghng ngy. +Khenthngccnhmlmvic c kt qu tt nht. +Phbnhrtkinhnghimcc nhm lm cha tt. + nh gi cho im bi thc hnh. - Cc nhm np bo co v nhn xt ln nhau. V.HNG DN V NH3 -Tiptctpomtskchthcnh:chiucaocacy,ngi nh - Gi sau mang dng c thc hnh tip - n li phn o n mt im m khng n c. NS:20/03/2011 NG:22/03/2011(8a, b) Tit 52 THC HNH(Tip) I.MC TIU 1.Kin thc: - Ti hin li cc trng hp ng dng ca tam gic. - Vn dng c cc trng hp ng dng ca tam gic thc hnh. 2.K nng: -Bitngdngtamgicngdngogintipcckhongcchtrong thc hnh. Gio n Hnh hc 8Nm hc 2011-2012 51 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton v thc hnh. II. DNG DY HC 1.GV: Thc, Thc o gc, gic k. Thc ngm, thc dy, giy bt. 2.HS:Thc, eke III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khi ng2 *Mc tiu: Kim tra s chun b ca HS v kin thc v dng c.. * dng: Thc, Gic k, thc ngm *Cch tin hnh: Hot ng ca GVHot ng cua HS -GV:okhongcchgiahai im trong c mt im khng th n c ta lm nh th no? - Kim tra s chun b ca HS Hot ng 2Hng dn HS thc hnh v thc hnh35 *Mc tiu: Hng dn HS thc hnh.. * dng: Thc, Gic k, thc ngm *Cch tin hnh: Bc 1:-GV:Nuyucucabuithc hnh +okhongcchgiahaiim trong cmtim khngthn c . + Phn chia 4 t theo 4 gc 4 v tr khc nhau. Bc 2: + Cc t n v tr qui nh tin hnh thc hnh.

A

Bc 1: Chnvtrtbngvchon thng BC c di tu . Bc 2: Dng gic k o cc gc - ABC= o ;- ACB = |Bc 3: VA A'B'C' trn giy sao choBC = a' ( T l vi a theo h s k) + - ABC= o ; - ACB = |Bc 4:o trn giy cnh A'B', A'C' ca A A'B'C' +TnhonAB,ACtrnthct theo t l k. Bc5:Bocoktqutnh Gio n Hnh hc 8Nm hc 2011-2012 52 -- --- -- - - -- -- -- o |B C GV yu cu HS Bo co kt qu c. HSthchnhocthctghi s liu. HStnhtontrngiytheot xch. HS bo co kt qu theo nhm. Hot ng 3Cng c v luyn tp5 *Mc tiu: Cng c v nhc nh HS v gi thc hnh. * dng: Thc, Gic k, thc ngm *Cch tin hnh: -GV:Kimtranhgioctnh ton ca tng nhm. - GV: lm vic vi c lp. +Nhnxt ktquoc catng nhm + Thng bo kt qu ng. +nghacavicvndngkin thctonhcvoisnghng ngy. Khen thngcc nhmlmvicc kt qu tt nht. +Phbnhrtkinhnghimcc nhm lm cha tt. + nh gi cho im bi thc hnh Cc nhm nhn xt ln nhau. Ch lng nghe kin ca GV. V.HNG DN V NH3 - Lm cc bi tp: 53, 54, 55 - n li ton b chng III - Tr li cu hi sgk. Gio n Hnh hc 8Nm hc 2011-2012 53 NS:22/03/2011 NG:24/03/2011(8a, b) Tit 53 N TP CHNG III I.MC TIU 1.Kin thc: - Ti hin li cc trng hp ng dng ca tam gic, Cng c v h thng ha kin thc ca chng. - Vn dng c cc trng hp ng dng ca tam gic tnh ton. 2.K nng: - Bit s dng my tnh vo tnh ton. 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, bng ph 2.HS:Thc, eke III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khi ng( n l thuyt)20 *Mc tiu: Ti hin v cng c kin thc c bn.. * dng: Thc, Bng ph *Cch tin hnh: Hot ng ca GVHot ng cua HS 1. Nu nh ngha on thng t l? I- L thuyt 1- on thng t l ' '' 'AB A BCD C D=2- nh l Talt trong tam gic Gio n Hnh hc 8Nm hc 2011-2012 54 2-Phtbiu.vhnh,ghiGT,KL ca nh l Talt trong tam gic? - Pht biu. v hnh, ghi GT,KL ca nh l Talt o trong tam gic? 3- Pht biu. v hnh, ghi GT KL h qu ca nh l Ta lt 4-Nutnhchtngphngic trong tam gic? 5-Nucctrnghpngdng ca 2 tam gic? A ABCca//BC ' ' ' ' ' '; ;' 'AB AC AB AC BB CCAB AC BB CC AB AC= = = 3- H qu ca nh l Ta lt ' ' ' ' AB AC B CAB AC BC= =4-Tnhchtngphngic trong tam gic Trong tam gic , ng phn gic ca1gcchiacnhidin thnh hai on thng t l vi hai cnh k hai on y. 5- Tam gic ng dng + 3 cnh tng ng t l + 1 gc xen gi hai cnh t l . + Hai gc bng nhau. Hot ng 2Hng dn HS lm bi tp v tnh ton22 *Mc tiu: Bit da vo cc trng hp ng dng ca tam gic tnh ton v da vo my tnh b ti. * dng: Thc, bng ph *Cch tin hnh: Cha bi 56 (5) - 1 HS ln bng cha bi tp Cha bi 57 (10) -GV:ChoHScubitonv tr li cu hi ca GV: + nhn xt v tr ca 3 im H, D, M trnonthngBCtacncvo yu t no? + Nhn xt g v v tr im D +Bnghnhvnhnxtgvvtr II- Bi tp Bi 56:T s ca hai on thng a)AB=5cm;CD=15cmth 5 115 3ABCD = =b) AB = 45 dm; CD = 150 cm = 15 dm th: 4515ABCD = =3;c)AB=5CD ABCD=5 Bi 57 A Gio n Hnh hc 8Nm hc 2011-2012 55 ca 3 im B, H, D + chng minh im H nm gia 2 im B, D ta cn chng minh iu g ? - HS cc nhm lm vic. - GV cho cc nhm trnh by v cht li cch CM. -GVnhclikinthccbn chng BH DMC AD l tia phn gic suy ra: DB ABDC AC= v AB < AC ( GT) => DB < DC=>2DC>DB+DC=BC=2MC+ DC >CMVy D nm bn tri im M. Mt khc ta li c: 902 2 2 2 2 2 2 2oA B CCAH C CA B C A B C| |= = + + | |\ .= + = +

V AC > AB => B > C=> B - C > 0 => 2B C > 0 T suy ra : 2 2A B CCAH= + > 2A VytiaADphinmgia2tia AHvACsuyraHnmbntri imD.TclHnmgiaBv D. V.HNG DN V NH3 - Lm cc bi tp cn li - n tpgi sau kim tra 45' Gio n Hnh hc 8Nm hc 2011-2012 56 NS: 24/03/2011 NG: 26/03/2011(8a, b) Tit 54KIM TRA 45 I. MC TIU 1. Kin thc: - Ti hin li cc trng hp bng nhau ca tam gic, tam gic vung v vn dng vo lm bi tp v tam gic ng dng v tnh ton. 2. K nng:- V c hnh v vit c gi thit, kt lun ca ni dung bi ton, c mt s k nng tnh ton khi tnh s o ca di.3. Thi : Nghim tc khi lm bi. II. HNH THC KIM TRA - Hnh thc: TNKQ kt hp t lun - HS lm bi ti lp. III. MA TRN

Cp Ch Nhn bit Thng Hiu Vn dng Tng Cp thpCp cao TNKQTLTNKQTLTNKQTL 1. Din tch hnh thang,din tcha gic -Vndngccc cng thc tnh din tch hc. -Bit cch tnh din tch ca cc hnh a gic li bngcchphnchia agicthnhcc tam gic. Gio n Hnh hc 8Nm hc 2011-2012 57 S cu :2 S im:C 1,C2 1,0 C8 1,5 3 2,5 =25% 2.nhl Ta-lttrong tam gic. -Hiuccnh ngha: T s ca hai on thng, cc on thng t l. -HiunhlTa-ltvtnh chtngphngicca tam gic. -Vndngcccnhl hc. S cu: 6 S im:C3 0,5 C7 2,0 2 2,5=25% 3.Tamgic ng dng -Hiunhnghahaitam gic ng dng. -Hiuccnhl v: + Cc trng hp ngdngcahai tam gic. + Cc trng hp ngdngcahai tam gic vung. S cu: 1 S im:C4,C5,C6 1,5 C9 3,5 4 5=50% Tng s cu Tngs im T l 3 2,5 25% 5 5,5 55% 1 2,0 20% 9 10 IV. KIM TRA A. TNKQ(3) Cu 1:Trong cc cng thc sau u l cng thc tnh din tch hnh thang? a)S = 12(a + b)h ; b) S = (a + b)h; c) S = (a + b):h; d) S = 12h (a + b) Cu2:Muntnhdintchcamtagictathnglmnhth no? a) Chia a gic thnh cc tam gic v tnh din tch ca cc tam gic. b) p dng cng thc tnh a gic c) Khng tnh c din tch ca a gic. d) Vn dng tt c cc trng hp trn. Gio n Hnh hc 8Nm hc 2011-2012 58 Cu 3: Nu mt ng thng song song vi mt cnh ca tam gic v hai cnh cn li th n nh ra trn hai cnh nhng on thng tng ng t l. Cu 4: Hai tam gic bng nhau th ng dng vi nhau ng hay sai? Cu 5: Hai tam gic ng dng vi nhau th bng nhau ng hay sai? Cu 6: Nu AABC # AMNP th AMNP # AABC ng hay sai? B. T LUN:(7) Cu 7: (1,5im) Tnh di x trong hnh v bn: Bit :AM = 6 cm ; AN = 4 cm NC = 2 cm ; MN ? BC

x246C BNMA Hnh 1 Cu 8: (2im) Tnh din tch hnh thang ABCD bit : AB = 20 cm ; CD = 40 cm v chiu cao h = AH = 15 cm.

4020h=15HDCBA Hnh 2 Cu 9: ( 3,5 im)Tnh cc di x, y ca cc on thng trong hnh sau: Gio n Hnh hc 8Nm hc 2011-2012 59

CEDB A23xy63,5 Hnh 3 V.HNG DN CHM A. TNKQ:( 3 im) Mi cu ng c 0,5 im. Cu123456 p naaCtS B.T LUN: (7 im) CuNi dungim 7 VMN ? BC, theo nh l Ta-lt ta c: NCANMBAM= hay 24 6=xx=346 . 2=1,5 8 Din tch hnh ch nht l: ADCT:S = 12 (a + b)h = 12 (20 + 40).15 = 450 (cm2) 2,0 9 V AB = 12 DE - B = - D (soletrong) - C 1 = - C 2(i nh) AABC ng dng viAEDC (g g) ABDE= ACEC= BCDC

Ta c : 3, 5x=36 x= 3.3, 56= 1,75 2y= 36 y =2.63= 4 0,5 0,5 0,5 0,5 0,75 0,75

VI. HNG DN V NH 1 -Chun b bi mi. Gio n Hnh hc 8Nm hc 2011-2012 60 NS:29/03/2011 NG:31/03/2011(8a, b) Tit 55 HNH HP CH NHT I.MC TIU 1.Kin thc: - Nhn bit c cc loi hnh hc v cc yu t ca chng - Vn dng c cc cng thc tnh din tch, th tch hc. 2.K nng: - Bit cch xc nh hnh khai trin ca cc hnh hc. 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khi ng(gii thiu v to tnh hung vo bi). 5 *Mc tiu: Gii thiu khi qut v kin thc ca chng. * dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng cua HS - Gv gii thiu khi qut v ni dung ca chng mi - GV da trn m hnh hnh hp ch nhtvtrnhnhvgiithiukhi nimhnhhpchnhtvhnh hp lp phng. - HS ch lng nghe Gio n Hnh hc 8Nm hc 2011-2012 61 Hot ng 2Hnh thnh khi nim hnh hp ch nht15 *Mc tiu: Hnh thnh c biu tng, nh ngha khi nim hnh hp ch nht* dng: Thc, bng ph *Cch tin hnh: Hnh hp ch nht: A B c cnh Mt nh Hnh lap phngD'C'B'A'DCBA GV:Hnhhpchnhtcbao nhiu nh mt cnh -EmhynuVDvmthnhhp chnhtgptrongisnghng ngy. -Hychracnh,mt,nhca hnh hp lp phng. -GV:Chohcsinhlmnhnxtv cht li. Hnhhpcsumtlhnhhp ch nht HnhlpphnglhnhhpCN c 6 mt l nhng hnh vung - GV cho hc sinh lm bi tp? - HS c yu cu bi ton 1- Hnh hp ch nht - HS ch ra: Hnh hp ch nht c + 8 nh + 6 mt + 12 cnh -HSchraVDtrongcucsng hng ngy l hnh hp - HS nhn xt tip. - HS c yu cu bi ton -HSlnbngchraccnh, cc cnh ( hoc dng phiu hc tp lm bi tp? ) Hot ng 3Mt phng v ng thng10 *Mc tiu: Bit u l mt phng, ng thng v ch ra c trn hnh v.* dng: Thc, bng ph *Cch tin hnh: 2. Mt phng v ng thng C Gio n Hnh hc 8Nm hc 2011-2012 62 -GV:Linhvinhngkhi nimbittronghnhhc phngccimA,B,CCc cnh AB, BC l nhng hnh g? - Cc mt ABCD; A'B'C'D' l mt phn ca mt phng ? hnh hop chnhatABCDA'B'C'D' -GV:Nurtnhcht:"ng thngiquahaiimthnm hon ton trong mt phng " * Cc nh A, B, C, l cc im *CccnhAB,BC,lcc on thng * Mi mt ABCD, A'B'C'D' l mt phn ca mt phng. - Hc sinh lm ra phiu hc tp( Nhp ) + Cc mt + Cc nh A,B,C l cc im +CccnhAB,BClccon thng. Hot ng 4Cng c v luyn tp13 *Mctiu:Bittshaingcao,tsdintchcahaitamgic ng dng * dng: Thc, bng ph *Cch tin hnh: -GV:ChoHSlmvictheonhm tr li bi tp 1, 2, 3 sgk/ 96,97 ChoHHCNc6mtulhnh ch nht -Cccnhbngnhaucahhcn ABCDA'B'C'D' l.. -NuOltrungimcaon thngBA'thOnmtrnon thng AB' khng? V sao?... -NuimKthuccnhBCth im K c thuc cnh C'D' khng ? hnh hop chnhatABCDA'B'C'D'

Gio n Hnh hc 8Nm hc 2011-2012 63 V.HNG DN V NH2 - Lm bi 4- ct bng ba cng ri ghp li NS:31/03/2011 NG:02/04/2011(8a, b) Tit 56 HNH HP CH NHT (Tip) I.MC TIU 1.Kin thc: - Nhn bit c cc loi hnh hc v cc yu t ca chng - Vn dng c cc cng thc tnh din tch, th tch hc. 2.K nng: - Bit cch xc nh hnh khai trin ca cc hnh hc. 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khing(Kimtravtotnhhungvo bi). 5 *Mc tiu: Ti hin li khi nim hnh hp ch nht. * dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng cua HS hnh hop chnhatABCDA'B'C'D'

Hyktnccmtcahnhhp ch nht? Gio n Hnh hc 8Nm hc 2011-2012 64 HS tr li Hot ng 2 Tmhiuvhaingthngsongsong trong khng gian20 *Mc tiu: Hnh thnh c biu tng, nh ngha khi nim hnh hp ch nht* dng: Thc, bng ph *Cch tin hnh: +AA'vBB'cnmtrongmtmt phng khng? C th niAA' // BB' ? v sao? +ADvBB'chaykhngcim chung? Haingthngkhngcim chung trong khng gian c c coi l//khng?bimitasnghin cu. 1.Haingthngsongsong trong khng gian. ?1.+Cvuthuchnhch nht AA'B'B +ADvBB'khngcim chung a // b a, b e mp () a b =C * V d: + AA' // DD' ( cng nm trong mp (ADD'A') + AD & DD' khng // v khng c im chung +AD&DD'khngcngnm trong mt mp hnh hop chnhatABCDA'B'C'D' * Ch : a // b; b // c a // c Hot ng 3 ngthngsongsongvimp&haimp song song 18 *Mctiu:Bitngtngsongsongvimpvhaimtphngsong song * dng: Thc, bng ph *Cch tin hnh: -GV:choHSquansthnhv bng v nu: 2.ngthngsongsongvi mp & hai mp song song hnh hop chnhatABCDA'B'C'D' BC// B'C ; BCkhng e (A'B'C'D') Gio n Hnh hc 8Nm hc 2011-2012 65 + BC c // B'C' khng? + BC c cha trong mp ( A'B'C'D') khng? -HStrlitheohngdnca GV - HS tr li bi tp ?3 +Hytmvingthngc quan h nh vy vi 1 mp no trong hnh v. chnh l ng thng // mp -GV:Giithiu2mp//bngm hnh +AB&ADctnhautiAv chng cha trong mp ( ABCD) + AB // A'B' v AD // A'D' ngha l AB,ADquanhvimpA'B'C'D' nh th no?+A'B'&A'D'ctnhautiA'v chngchatrongmp(A'B'C'D') th ta ni rng: mp ABCD // mp (A'B'C'D') ?3 + AD // (A'B'C'D') + AB // (A'B'C'D') + BC // (A'B'C'D') + DC // (A'B'C'D') * Ch : ng thng song song vi mp: BC // mp (A'B'C'D')BC// B'C'

BCe(A'B'C'D') LKHIAA'BB'CC'DD' * Hai mp song song mp (ABCD) // mp (A'B'C'D') a // a' b // b' a b ; a' b' a', b' c mp (A'B'C'D') a, bcmp ( ABCD) ?4 : mp (ADD/A/ )// mp (IHKL ) mp (BCC/B/ )// mp (IHKL ) mp (ADD/A/ )// mp (BCC/B/) mp (AD/C/B/ )// mp (ADCB ) 3)Nhnxt:-a//(P)thav(P) khngcimchung-(P)//(Q) (P) v (Q) khng c im chung- (P) v(Q) c 1 im chung A th c ngthngachungiquaA (P) (Q) Gio n Hnh hc 8Nm hc 2011-2012 66 -GVnhclicckhinimt// mp, 2 mp //, 2 mp ct nhau V.HNG DN V NH2 - Lm cc bi tp 7,8 sgk NS:05/04/2011 NG:07/04/2011(8a, b) Tit 57TH TCH HNH HP CH NHT

I.MC TIU 1.Kin thc: - Nhn bit c cc loi hnh hc v cc yu t ca chng - Vn dng c cc cng thc tnh din tch, th tch hc. 2.K nng: - Bit cch xc nh hnh khai trin ca cc hnh hc. -Nhn bit c cc kt qu c phn nh trong hnh hp ch nht v quan h song song v quan h vung gc gia cc i tng ng thng, mt phng. 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khing(Kimtravtotnhhungvo bi). 5 *Mc tiu: Ti hin li khi nim hnh hp ch nht. * dng: Thc. *Cch tin hnh: Gio n Hnh hc 8Nm hc 2011-2012 67 Hot ng ca GVHot ng cua HS hnh hop chnhatABCDA'B'C'D'

-Hyktnccngthngsong song vi mt phng (ABCD)? V cc mtphngsongsongvi mp(ABCD)? HS tr li da vo hnh v. Hot ng 2 ng thng vung gc vi mt phng - Hai mt phng vung gc 18 *Mc tiu: K c ng thng vung gc vi mt phng v hai mt phng vung gc.* dng: Thc, bng ph *Cch tin hnh: - HS tr li ti ch bi tp ?1 Hnh 84acbD' C'B'A'DCBA GV: cht li ng thng mp aa' ; bb' amp (a',b')a' ct b' -GV:Hytmtrnmhnhhoc hnhvnhngvdvng thng vung gc vi mp? - HS tr li theo hng dn ca GV -HSphtbiuthnol2mp vung gc? - HS tr li theo hng dn ca GV 1. ng thng vung gc vi mtphng.Haimtphng vung gc ?1 AA' ADvAA'DD'lhnhch nht AA' ABvAA'B'Blhnhch nht Khitani:A/Avunggcvi mtphng(ABCD)tiAvk hiu : A/A mp ( ABCD ) * Ch : + Nu acmp(a,b); amp(a',b') th mp (a,b)mp(a',b') * Nhn xt: SGK/ 101 ?2 CB/B,C/C,D/Dvunggcmp (ABCD ) C B/B (ABCD) Gio n Hnh hc 8Nm hc 2011-2012 68 -GV:tiuhctahccng thc tnh th tch ca hnh hp ch nht. Hy nhc li cng thc ? -Nulhnhlpphngthcng thc tnh th tch s l g? B/B c mp (B/BCC' ) Nnmp(B/BCC')mp (ABCD) C/m t2:mp (D/DCC' ) mp (ABCD) mp (D/DAA' ) mp (ABCD) V = a.b.c Vlp phng = a3 Hot ng 3 Th tch hnh hp ch nht 10 *Mc tiu: tnh c th tch ca hnh hp ch nht theo cng thc. * dng: Thc, bng ph *Cch tin hnh: GVyucuHScSGKtr102-103phnthtchhnhhpch nhtncngthctnhthtch hnh hp ch nht * V d: + HS ln bng lm VD 2) Th tch hnh hp ch nht VHnh hp CN= a.b.c( Vi a, b, c l 3 kch thc ca hnh hp ch nht ) Vlp phng = a3 S mi mt = 216 : 6 = 36 + di ca hnh lp phnga =36 = 6 V = a3 = 63 = 216 Hot ng 4 Cng c v luyn tp 10 *Mc tiu: Cng c li kin thc v vn dng vo lm bi tp* dng: Thc, bng ph *Cch tin hnh: Gio n Hnh hc 8Nm hc 2011-2012 69 -GvyucuHScvlmbi tp 10 ( trang 103 sgk) - Gi 1 HS ln bng thc hin giI bi tp. Hnh 91HGFEDCBA - GV cht li kin thc c bn ca bi Bi 10 SGK HS : a) BFEF v BFFG( t/c HCN) do : BF (EFGH) b)DoBF(EFGH)mBF c(ABFE) (ABFE)(EFGH) *DoBF(EFGH)mBF c(BCGF) (BCGF)(EFGH) HS nhn xt. V.HNG DN V NH2 - Lm cc bi tp 11, 12, 13 v xem phn luyn tp - Gi bi 11: Gi cc kch thc ca hnh hp ch nht l a, b, c Ta c: 3 4 5a b c= = = k Suy ra a= 3k ; b = 4k ; c =5kV = abc = 3k. 4k. 5k = 480 Do k = 2 Vy a = 6; b = 8 ; c = 10 NS:07/04/2011 NG:09/04/2011(8a, b) Tit 58 LUYN TP

I.MC TIU 1.Kin thc: - Nhn bit c cc loi hnh hc v cc yu t ca chng - Vn dng c cc cng thc tnh din tch, th tch hc. Ti hin li kin thc v hnh hp ch nht v cng thc tnh din tch, th tch. - Vn dng c cc cng thc tnh din tch, th tch hc. 2.K nng: -Nhn bit c cc kt qu c phn nh trong hnh hp ch nht v quan h song song v quan h vung gc gia cc i tng ng thng, mt phng. Gio n Hnh hc 8Nm hc 2011-2012 70 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khing(Kimtravtotnhhungvo bi). 5 *Mc tiu: Ti hin li kin thc v hnh hp ch nht. * dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng cua HS -Nhcliphngphpdng chng minh 1 ng thng mp amp(a'b') + Nhc li ng thng // mp BC// mp (A'B'C'D') HS tr li : 1 ng thng mp amp(a'b') aa' ; ab' a' ct b' + Nhc li ng thng // mp BC// mp (A'B'C'D') BC // B'C' BCcmp(A'B'C'D') Hot ng 2 Bi tp vn dng cng thc tnh th tch ca hnh hp ch nht 37 *Mc tiu: Vn dng c cng thc tnh th tch vo lm bi tp.* dng: Thc, bng ph *Cch tin hnh: - GV yu cu HS lm bi tp 13v 1 HS ln thc hin ( sgk-104) Hnh 89ABCDMNP Q - GV gi HS khc nhn xt. - Gv yu cu HS lm bi tp v gi 1HSlnbngchabi14(sgk-HS cha bi 1) Cha bi 13/104 Di22181520 Rng 1451113 Cao5688 Sy30890165260 Gio n Hnh hc 8Nm hc 2011-2012 71 104) - GV gi HS khc nhn xt? V GV cha li. - Gv yu cu HS lm bi tp v gi 1HSlnbngchabi15(sgk-104) - GV gi HS khc nhn xt? V GV cha li. V22181520 - HS nhn xt. HS : 2) Cha bi 14/104 a) Th tch nc vo: 120. 20 = 2400 (lt) = 2,4 m3 Din tch y b l: 2,4 : 0,8 = 3 m2

Chiu rng ca b nc: 3 : 2 = 1,5 (m) b) Th tch ca b l: 20(120+60)=3600(l)=3,6 m3 Chiu cao ca b l:3,6 : 3 = 1, 2 m - HS nhn xt. 3) Cha bi 15/104 HS: Gii: Khichathgchvonc cch ming thng l: 7 - 4 = 3 dm Thtchncvgchtng bng th tch ca 25 vin gch 2 .1. 0,5. 25 = 25 dm3 Din tch y thng l: 7. 7. = 49 dm3 Chiu cao nc dng ln l: 25 : 49 = 0, 51 dm Saukhithgchvonccn cch ming thng l: 3- 0, 51 = 2, 49 dm V.HNG DN V NH3 Hc thuc cng thc tnh th tch, din tch cc hnh hc v lm bi tp 17 (sgk-105) Gio n Hnh hc 8Nm hc 2011-2012 72 Gi : Da vo hnh v k tn. NS:12/04/2011 NG:14/04/2011(8a, b) Tit 59 HNH LNG TR NG

I.MC TIU 1.Kin thc: -Nhn bit c cc loi hnh hc v cc yu t ca chng. 2.K nng: -Bit cch xc nh hnh khai trin ca cc hnh hc.3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khing(Kimtravtotnhhungvo bi). 2 *Mc tiu: To tnh hung vo bi. * dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng cua HS -Chicnlngtr106chotahnh nh mt lng tr ng. Em hy quan st hnh xem y ca n l hnh g ? cc mt bn l hnh g ? -HS ch lng nghe Hot ng 2Tm hiu Hnh lng tr ng 15 *Mc tiu: Bit hnh lng tr ng v ch ra c cc nh, mt, cnh. * dng: Thc, bng ph, hnh lng tr ng. *Cch tin hnh: Gio n Hnh hc 8Nm hc 2011-2012 73 - GV: a ra hnh lng tr ng v gii thiu Hnhchnht,hnhvunglcc dngcbitcahnhbnhhnh nnhnhhpchnht,hnhlp phngcnglnhnglngtr ng. GV aramts mhnhlng tr ng ng gic, tam gic chrccy,mtbn,cnhbn ca lng tr. 1.Hnh lng tr ng + A, B, C, D, A1, B1, C1, D1 L cc nh + ABB1A1; BCC1B1 ... cc mt bn l cc hnh ch nht +onAA1,BB1,CC1//v bng nhau l cc cnh bn +Haimt:ABCD,A1B1C1D1l hai y +dicnhbncgil chiu cao +yltamgic,tgic,ng gic ta gi l lng tr tam gic, lng tr t gic, lng tr ng gic +Ccmtbnlcchnhch nht + Hai y ca lng tr l 2 mp //. Hnh 93ABCDA1B1C1D1 ?1 A1A AD(vADD1A1lhnh ch nht ) A1A AB(vADB1`A1lhnh ch nht ) MABvADl2ngthng ct nhau ca mp ( ABCD) Suy ra A1A mp (ABCD ) C/ m T2: A1A mp (A1B1C1D1 ) Ccmtbncvunggcvi hai mt phng y *Hnhlngtrngcyl hnhbnhhnhcgilhnh hp ng Tronghnhlngtrngcc cnhbn//vbngnhau,cc mt bn l cc hnh ch nht. Hot ng 3Tm hiu v cc v d 25 *Mc tiu: Vn dng c kin thc mi hc vo lm phn v d.* dng: Thc, bng ph, hnh lng tr ng. Gio n Hnh hc 8Nm hc 2011-2012 74 *Cch tin hnh: Hnh 95hABCD EF GVarahnhvvyucuHS tr li cu hi m GV a ra. GV cht li ch SGK Gv gi HS nhn xt. - GV cho HS lm bi tp 19 sgk cng c kin thc mi hc. 2.V d ABCA/B/C/lmtlngtrng tam gic Haiylnhngtamgicbng nhau Ccmtbnlnhnghnhch nht di mt cnh bn c gi l chiu cao 2) Ch : - Mt bn l HCN: Khi v ln mp ta thng v thnh HBH - Cc cnh bn v // -Cccnhvunggccthv khng vung gc HS nhn xt. HS lm bi 19 (sgk-108) V.HNG DN V NH3 +Hc bi c+Lm cc bi tp 19, 22 sgk +Tp v hnh. Gio n Hnh hc 8Nm hc 2011-2012 75 NS:14/04/2011 NG:16/04/2011(8a, b) Tit 60DIN TCH XUNG QUANH CA HNH LNG TR NG

I.MC TIU 1.Kin thc: -Nhn bit c cc loi hnh hc v cc yu t ca chng. 2.K nng: - Vn dng c cc cng thc tnh din tch, th tch hc. -Bit cch xc nh hnh khai trin ca cc hnh hc.3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khing(Kimtravtotnhhungvo bi). 2 *Mctiu:Tihinlikinthcvhnhlngtrngvtotnh hung vo bi. * dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng cua HS tvn:Quabichacabn cnhnxtgvdintchHCN: AA'B'Bivihnhlngtrng ADCBEG Din tch c ngha g? Vydintchxungquanhhnhlng tr ng tnh nh th no? HS ch lng nghe. Hot ng 2 Tmhiucngthctnhdintchxung quanh. 15 Gio n Hnh hc 8Nm hc 2011-2012 76 *Mc tiu: Bit cng thc tnh din tch xung quanh.* dng: Thc, bng ph, hnh lng tr ng. *Cch tin hnh: - GV: Cho HS lm bi tp ?1 Quansthnhkhaitrincahnh lng tr ng tam gic + di cc cnh ca 2 y l: 2,7 cm; 1,5 cm; 2 cm * HS lm bi tp ? 1)Cngthctnhdintch xung quanh ?1 * HS lm bi tp ? - Din tch AA'B'B = ? - So snh n vi hnh lng tr t suy ra cng thc tnh din tch xungquanhcahnhlngtr ng: + di cc cnh ca 2 y l: 2,7 cm; 1,5 cm; 2 cm +Dintchcahnhchnht th nht l: 2,7 . 3 = 8,1 cm2 +Din tch ca hnh ch nht th hail: 1,5 . 3 = 4,5cm2 +Din tch ca hnh ch nht th bal: 2 . 3 = 6cm2 +Tngdintchcacbahnh ch nht l: 8,1 + 4,5 + 6 = 18,6 cm2

* Din tch ton phn : Stp= Sxq + 2 S y Hot ng 3Tm hiu v v d 25 *Mc tiu: Vn dng c kin thc mi hc vo lm phn v d.* dng: Thc, bng ph, hnh lng tr ng. *Cch tin hnh: Cholngtrngtamgic ABCDEG sao choADC vung C cAC=3cm,AB=6cm,CD=4 2. V d Tnh Stp7cm4cm3cm Gio n Hnh hc 8Nm hc 2011-2012 77 cmthdintchxungquanhlbao nhiu? GV gi HS c bi ? tnhdintchtonphnca hnhlngtrtacntnhcnhno na? Tnh din tch xung quanh ca hnh lng tr? Tnh din tch hai y Tnhdintchtonphncahnh lng tr AADC vung C c: AD2 = AC2 + CD2

= 9 + 16 = 25 AD = 5 Sxq = ( 3 +4 + 5). 6 = 72; S2 = 3 . 4 = 12 Stp = 72 + 12 = 84 cm2 Hot ng 4Luyn tp5 *Mc tiu: Vn dng c kin thc mi hc vo lm bi tp* dng: Thc, bng ph, hnh lng tr ng. *Cch tin hnh: GV treo bng ph bi tp ? Yu cu HS hot ng nhmThi gian hot ng nhm 7 pht GV treo bng ph ca cc nhm Cho cc nhm nhn xt cho GV cht a li gii chnh xc Bi 23/ SGK 111 a) Hnh hp ch nhtSxq = ( 3 + 4 ). 2,5 = 70 cm2 2S = 2. 3 .4 = 24cm2 Stp = 70 + 24 = 94cm2 b) Hnh lng tr ng tam gic: CB = 2 22 3 13 + =( nh l Pi Ta Go ) Sxq = ( 2 + 3 +13) . 5= 5 ( 5 + 13) = 25 + 5 13(cm 2)2S =2. 12 . 2. 3 = 6 (cm 2)Stp=25+5 13+6= 31+ 5 13(cm 2) Gio n Hnh hc 8Nm hc 2011-2012 78 V.HNG DN V NH3 HS lm cc bi tp 25, 26 HD:xemcgpchaykhngdatrnnhngyutno? nh no trng nhau, cnh no trng nhau sau khi gp. NS:19/04/2011 NG:21/04/2011(8a, b) Tit 61 TH TCH HNH LNG TR NG

I.MC TIU 1.Kin thc: -Nhn bit c cc loi hnh hc v cc yu t ca chng. 2.K nng: - Ch ra c nh,cnh, cc mt ca hnh chp, ng cao ca hnh chp. 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke, c trc bi nh. III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khing(Kimtravtotnhhungvo bi). 2 *Mc tiu: Ti hin li kin thc v th tch ca hnh lng tr ng v to tnh hung vo bi. * dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng cua HS tvn:GVamhnhhnh chp v gii thiu : - Mt y l a gic, mt bn l tam gic c chung 1 nh, nh chung gi l nh ca hnh chp ? So snh hnh chp v hnh lng tr HS ch lng nghe. HS nghe GV gii thiu Gio n Hnh hc 8Nm hc 2011-2012 79 Hnh 116chieu caomat benmat ayng GVahnhvvyucuHSv vo v Hnh 116chieu caomat benmat ay GV yu cu HS c tn nh, ng cao, cnh bn, mt bn, mt y GVgiithiucchgitn,khiu hnh chp theo a gic y So snh 2 khI nim 2 hnh HS quan st tr li : - nh:S - Cnh bn : SA, SB, SC, SD - ng cao : SH -Mtbn:SAB,SBC,SCD, SDA - Mt y : ABCD Hot ng 2Tm hiu v hnh chp 10 *Mc tiu: Hnh thnh khi nim hnh chp cho HS. * dng: Thc, bng ph, hnh chp. *Cch tin hnh: GVamhnhgiithiuhnh chpulhnhcmtyla gicu,ccmtbnlcctam gic cn bng nhau c chung nh - GV cho hs quan st m hnh hnh chptgicu,tamgicuv yucuhsnhnxtmty,mt bn -GVahnh117/SGKlnmn hnhchohsquanst=>nucch v ? Sauhngdnhsvtheocc bc : +)Vylhnhvung(vhnh khng gian : v hnh bnh hnh) +)V2ngchoytgic vngcao:tgiao2ng cho 1. Hnh Chp HS ch lng nghe v tr li Gio n Hnh hc 8Nm hc 2011-2012 80 +)Trnngcaoly1imS (lnhhnhchp)niSvi cc nh hnh vung y Hot ng 3Hnh chp u 25 *Mc tiu: Bit khi nim hnh chop u* dng: Thc, bng ph. *Cch tin hnh: +) Ly I l trung im BC ni SI : SI l trung on ca hnh chp ? Trung on c vung gc vi mt phng y khng ? -ChoHSquansthnhkhaitrin cachptamgicuvlm?/ SGK 2)Hnh chp uHnh 117Canh benTrung oanMat ayMat benng caonh HS:trungonchvunggc vi1cnhychpkhng vung gc vi mt phng y 2 hs ln bng lm ? Hot ng 4Hnh chp ct u5 *Mc tiu: Bit hnh chp ct u* dng: Thc, bng ph, hnh lng tr ng. *Cch tin hnh: V.HNG DN V NH3 - Hng dn bi 28: y l hnh g? chiu cao ? suy ra th tch? Da vo nh ngha xc nh y. - Hng dn bi 30 Phn c:Phn chiahpl c2hnhc th pdng cng thctnh thtch c. Gio n Hnh hc 8Nm hc 2011-2012 81 NS:21/04/2011 NG:23/04/2011(8a, b) Tit 62 LUYN TP

I.MC TIU 1.Kin thc: -Ti hin li cng thc tnh th tch ca hnh lng tr ng, Nhn bit c cc loi hnh hc v cc yu t ca chng. 2.K nng: - Vn dng c cc cng thc tnh din tch, th tch ca hnh lng tr ng. 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke, c trc bi nh. III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khing(Kimtravtotnhhungvo bi). 2 *Mc tiu: Ti hin li kin thc v th tch ca hnh lng tr ng v to tnh hung vo bi. * dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng cua HS -Kim tra bi c: Nu cng thc tnh th tch ca hnh lng tr ng? -GVgiHSkhcnhnxtvcho im - HS nu ng thc tnh th tch. Hot ng 2 Bi tp Vn dng cng thc tnh th tch in vo bng. 15 *Mc tiu: Vn dng cng thc tnh th tch ca hnh lng tr ng.* dng: Thc, bng ph. Gio n Hnh hc 8Nm hc 2011-2012 82 *Cch tin hnh: -GVcvinvotrongtrng cho thch hp Gi HS ln bng thc hin Gi HS nhn xt v GV cha li bi tp HS:3) Cha bi 31 LT1LT2LT3 C.caohnh lngtr ng570,003C.caoca tamgic y 4 145 5 Cnhng vi 35 6Dintch y 6 715 Thtch hnhlng tr ng 30 49 0,045l HS nhn xt. Hot ng 3Bi tp c hnh v v tnh th tch 25 *Mc tiu: Vn dng c kin thc lm bi tp.* dng: Thc, bng ph. *Cch tin hnh: GVyucuHScvlmbi tp gi 1 HS ln bng thc hin GV gi HS khc nhn xt. GV cha li

2) Cha bi 34 ( sgk) HS thc hin: SABC = 12 cm2

a) S = 28 cm2 ; h = 8 V = S. h = 28. 8 = 224 cm3 b) SABC = 12 cm2 ; h = 9 cm V = S.h = 12 . 9 = 108 cm3 HS nhn xt. Gio n Hnh hc 8Nm hc 2011-2012 83 -GVnghHSlmbitp35 (sgk-116) Hnh 1154cm8cm3cm GVyucu1HSlnbngthc hin Gi HS khc nhn xt 3.Bi tp 35 ( sgk-116) HS : Din tch y l: ( 8. 3 + 8. 4) : 2 = 28 cm2 V = S. h = 28. 10 = 280 cm3 C th phn tch hnh lng tr thnh 2 hnh lng tr tam gic c din tch y ln lt l12 cm2 v 16 cm2 ri cng hai kt qu) HS nhn xt. V.HNG DN V NH3 - HS lm bi tp 33 sgk -Hc bi c, tp v hnh. Hng dn bi tp 32 v nh: - S = ? cm2 - V lng tr =? cm3 - Khi lng li ru m = V. D NS:19/05/2011 Gio n Hnh hc 8Nm hc 2011-2012 84 NG:21/05/2011(8a, b) Tit 63 HNH CHP U V HNH CHP CT U

I.MC TIU 1.Kin thc: -Nhn bit c cc loi hnh hc v cc yu t ca chng. 2.K nng: - Ch ra c nh,cnh, cc mt ca hnh chp, ng cao ca hnh chp. 3.Thi : -Tch cc, hp tc, cn thn khi tnh ton. II. DNG DY HC 1.GV: Thc, eke, bng ph 2.HS:Thc, eke, c trc bi nh. III.PHNG PHP -Vn p, gi m, tch cc ha hot ng ca HS. IV.T CHC DY HC Hot ng 1Khing(Kimtravtotnhhungvo bi). 2 *Mc tiu: Ti hin li kin thc v th tch ca hnh lng tr ng v to tnh hung vo bi. * dng: Thc. *Cch tin hnh: Hot ng ca GVHot ng cua HS tvn:GVamhnhhnh chp v gii thiu : - Mt y l a gic, mt bn l tam gic c chung 1 nh, nh chung gi l nh ca hnh chp ? So snh hnh chp v hnh lng tr ng GVahnhvvyucuHSv vo v Hnh 116chieu caomat benmat ay GV yu cu HS c tn nh, ng cao, cnh bn, mt bn, mt y GVgiithiucchgitn,khiu hnh chp theo a gic y HS ch lng nghe. HS nghe GV gii thiu So snh 2 khI nim 2 hnh HS quan st tr li : Gio n Hnh hc 8Nm hc 2011-2012 85 Hnh 116chieu caomat benmat ay - nh:S - Cnh bn : SA, SB, SC, SD - ng cao : SH -Mtbn:SAB,SBC,SCD, SDA - Mt y : ABCD Hot ng 2Tm hiu v hnh chp 10 *Mc tiu: Hnh thnh khi nim hnh chp cho HS. * dng: Thc, bng ph, hnh chp. *Cch tin hnh: GVamhnhgiithiuhnh chpulhnhcmtyla gicu,ccmtbnlcctam gic cn bng nhau c chung nh - GV cho hs quan st m hnh hnh chptgicu,tamgicuv yucuhsnhnxtmty,mt bn -GVahnh117/SGKlnmn hnhchohsquanst=>nucch v ? Sauhngdnhsvtheocc bc : +)Vylhnhvung(vhnh khng gian : v hnh bnh hnh) +)V2ngchoytgic vngcao:tgiao2ng cho +)Trnngcaoly1imS (lnhhnhchp)niSvi cc nh hnh vung y 1. Hnh Chp HS ch lng nghe v tr li Hot ng 3Hnh chp u 25 *Mc tiu: Bit khi nim hnh chop u* dng: Thc, bng ph. *Cch tin hnh: +) Ly I l trung im BC ni SI : SI l trung on ca hnh chp ? Trung on c vung gc vi mt phng y khng ? 2)Hnh chp uHnh 117Canh benTrung oanMat ayMat benng caonh Gio n Hnh hc 8Nm hc 2011-2012 86 -ChoHSquansthnhkhaitrin cachptamgicuvlm?/ SGK HS:trungonchvunggc vi1cnhychpkhng vung gc vi mt phng y 2 hs ln bng lm ? Hot ng 4Hnh chp ct u5 *Mc tiu: Bit hnh chp ct u* dng: Thc, bng ph, hnh lng tr ng. *Cch tin hnh: GVchohsquanstmhnhhnh chp ct u ChohsquansthnhvSGKv hi?ychpct-cimmt y ? Mt bn l hnh g ? HS:Mtylccagicu nm trn 2 mt phng song song - Mt bn l cc hnh thang cn V.HNG DN V NH3 GV Cho hs lm bi tp 36/SGKYu cu hs quan st hnh trn mn hnh ri in . * HD v nh - Lm bi tp 37, 38, 39 / SGK HDhs lm bi 38: - Ct gp hnh nh hnh 123 / SGK hc bisau