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Holt Geometry 4-1 Classifying Triangles 4-1 Classifying Triangles Holt Geometry Warm Up Warm Up Lesson Lesson Presentation Presentation Lesson Quiz Lesson Quiz

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4-1. Classifying Triangles. Holt Geometry. Warm Up. Lesson Presentation. Lesson Quiz. Do Now Classify each angle as acute, obtuse, or right. 1. 2. 3. 4. If the perimeter is 47, find x and the lengths of the three sides. Objectives. - PowerPoint PPT Presentation

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Holt Geometry

4-1 Classifying Triangles4-1 Classifying Triangles

Holt Geometry

Warm UpWarm Up

Lesson PresentationLesson Presentation

Lesson QuizLesson Quiz

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Holt Geometry

4-1 Classifying Triangles

Do NowClassify each angle as acute, obtuse, or right.

1. 2.

3.

4. If the perimeter is 47, find x and the lengths of the three sides.

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Holt Geometry

4-1 Classifying Triangles

TSW classify triangles by their angle measures and side lengths.

TSW use triangle classification to find angle measures and side lengths.

Objectives

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Holt Geometry

4-1 Classifying Triangles

acute triangleequiangular triangleright triangleobtuse triangleequilateral triangleisosceles trianglescalene triangle

Vocabulary

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Holt Geometry

4-1 Classifying Triangles

Recall that a triangle ( ) is a polygon with three sides. Triangles can be classified in two ways: by their angle measures or by their side lengths.

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Holt Geometry

4-1 Classifying Triangles

B

AC

AB, BC, and AC are the sides of ABC.

A, B, C are the triangle's vertices.

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Holt Geometry

4-1 Classifying Triangles

Acute Triangle

Three acute angles

Triangle Classification By Angle Measures

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Holt Geometry

4-1 Classifying Triangles

Equiangular Triangle

Three congruent acute angles

Triangle Classification By Angle Measures

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Holt Geometry

4-1 Classifying Triangles

Right Triangle

One right angle

Triangle Classification By Angle Measures

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Holt Geometry

4-1 Classifying Triangles

Obtuse Triangle

One obtuse angle

Triangle Classification By Angle Measures

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Holt Geometry

4-1 Classifying Triangles

Classify BDC by its angle measures.

Example 1: Classifying Triangles by Angle Measures

Classify ABD by its angle measures.

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Holt Geometry

4-1 Classifying Triangles

Classify FHG by its angle measures.

Example 2

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Holt Geometry

4-1 Classifying Triangles

Equilateral Triangle

Three congruent sides

Triangle Classification By Side Lengths

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Holt Geometry

4-1 Classifying Triangles

Isosceles Triangle

At least two congruent sides

Triangle Classification By Side Lengths

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Holt Geometry

4-1 Classifying Triangles

Scalene Triangle

No congruent sides

Triangle Classification By Side Lengths

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Holt Geometry

4-1 Classifying Triangles

Remember!When you look at a figure, you cannot assume segments are congruent based on appearance. They must be marked as congruent.

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Holt Geometry

4-1 Classifying Triangles

Classify EHF by its side lengths.

Example 3: Classifying Triangles by Side Lengths

Classify EHG by its side lengths.

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Holt Geometry

4-1 Classifying Triangles

Classify ACD by its side lengths.

Example 4

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Holt Geometry

4-1 Classifying Triangles

Find the side lengths of JKL.

Example 5: Using Triangle Classification

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Holt Geometry

4-1 Classifying Triangles

Find the side lengths of equilateral FGH.

Example 6

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Holt Geometry

4-1 Classifying Triangles

A steel mill produces roof supports by welding pieces of steel beams into equilateral triangles. Each side of the triangle is 18 feet long. How many triangles can be formed from 420 feet of steel beam?

Example 7: Application

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Holt Geometry

4-1 Classifying Triangles

Each measure is the side length of an equilateral triangle. Determine how many 7 in. triangles can be formed from a 100 in. piece of steel.

Example 8

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Holt Geometry

4-1 Classifying Triangles

Each measure is the side length of an equilateral triangle. Determine how many 10 in. triangles can be formed from a 100 in. piece of steel.

Example 9

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Holt Geometry

4-1 Classifying Triangles

Lesson Quiz

Classify each triangle by its angles and sides.

1. MNQ

2. NQP

3. MNP

4. Find the side lengths of the triangle.

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Holt Geometry

4-1 Classifying Triangles

Lesson Quiz

Classify each triangle by its angles and sides.

1. MNQ

2. NQP

3. MNP

4. Find the side lengths of the triangle.

acute; equilateral

obtuse; scalene

acute; scalene

29; 29; 23