Find the perimeter of isosceles ∆KLM with base 𝐾𝐿 given LM = 12 – d, KM = 4d – 13, and KL = d + 6. Problem of the Day

Section 4-2 Angles of Triangles

Then Now Objectives You classified triangles by their side or angle measures. Apply the Triangle Angle-Sum Theorem. Apply Exterior Angle Theorem.

Common Core State Standards Content Standards G.CO.10 – Prove theorems about triangles. Mathematical Practices 1) Make sense of problems and persevere in solving them. 3) Construct viable arguments and critique the reasoning of others. Common Core State Standards

Triangle Angle-Sum Theorem

Find the measure of each numbered angle. Example 1

Find the measure of each numbered angle. Example 1

In addition to its three interior angles, a triangle can have exterior angles formed by one side of the triangle and the extension of an adjacent side. Each exterior angle of a triangle has two remote interior angles that are not adjacent to the exterior angle. Vocabulary

Exterior Angle Theorem

Tanya mounts the shelving bracket shown to the wall of her closet Tanya mounts the shelving bracket shown to the wall of her closet. What is the measure of ∠1, the angle that the bracket makes with the wall? Example 2

Find x and m∠ABC. Example 2

Find m∠F. Example 2

Triangle Angle-Sum Corollaries

Find the measures of each numbered angle. ∠1 ∠2 ∠3 ∠4 Example 3

Find the measures of each numbered angle. ∠1 ∠2 ∠3 ∠4 ∠5 Example 3

p.250 #9 – 11, 21, 22, 30 – 32, 38 Homework