Warm Up 5-1 Classify each angle as acute, obtuse, or right. 1. 2. 3. 1. 2. 3. 4. If the perimeter is 47, find x and the lengths of the three sides.

Classify triangles by their angle measures and side lengths. 5-1 Learning Objectives Classify triangles by their angle measures and side lengths. Use triangle classification to find angle measures and side lengths.

5-1 A triangle ( ) is a polygon with three sides. Triangles can be classified in two ways: (1) by angle measures (2) or by side lengths.

Acute triangle Scalene Equiangular Isosceles Right Equilateral Obtuse 5-1 By angle measure By side length Acute triangle Scalene Equiangular Isosceles Right Equilateral Obtuse

Acute Triangle Three acute angles Triangle Classification 5-1 Triangle Classification By Angle Measures Acute Triangle Three acute angles

Three congruent acute angles 5-1 Triangle Classification By Angle Measures Equiangular Triangle Three congruent acute angles

Right Triangle One right angle Triangle Classification 5-1 Triangle Classification By Angle Measures Right Triangle One right angle

Obtuse Triangle One obtuse angle Triangle Classification 5-1 Triangle Classification By Angle Measures Obtuse Triangle One obtuse angle

Example 1A: Classifying Triangles by Angle Measures 5-1 Example 1A: Classifying Triangles by Angle Measures 1 2 3 4

Equilateral Triangle Three congruent sides Triangle Classification 5-1 Triangle Classification By Side Lengths Equilateral Triangle Three congruent sides

At least two congruent sides 5-1 Triangle Classification By Side Lengths Isosceles Triangle At least two congruent sides

Scalene Triangle No congruent sides Triangle Classification 5-1 Triangle Classification By Side Lengths Scalene Triangle No congruent sides

Example 1B: Classifying Triangles by Side length 5-1 Example 1B: Classifying Triangles by Side length 2) 1) 3)

How to classify triangles in a coordinate plane? 5-1 How to classify triangles in a coordinate plane? 1. Find the coordinates. 2. Use the distance formula to find the length. 3. Compare the length of each side of the triangle. “I DO” “You do w/partner” “You alone”

Summary about triangles 5-1 Summary about triangles

5-1 Angles! Triangles have interior angles and exterior angles.

5-1 Angles! The sum of interior angles

Find the measure of x and classify the triangles 5-1 Find the measure of x and classify the triangles “I DO” 1

Find the measure of x and classify the triangles 5-1 Find the measure of x and classify the triangles “We do” 2

Find the measure of x and classify the triangles 5-1 Find the measure of x and classify the triangles “You w/partner” 3

Find the measure of x and classify the triangles 5-1 Find the measure of x and classify the triangles “You alone” 4

Exterior Angle Theorem 5-1 Exterior Angle Theorem

Exterior Angle Theorem Examples 5-1 Exterior Angle Theorem Examples “I DO” 1

Exterior Angle Theorem Examples 5-1 Exterior Angle Theorem Examples “We Do” 2

Exterior Angle Theorem Examples 5-1 Exterior Angle Theorem Examples “You with a Partner” 3

Exterior Angle Theorem Examples 5-1 Exterior Angle Theorem Examples “You Alone” 3