Triangle sum and exterior angles Unit 1 lesson 2 Triangle sum and exterior angles

Objective Use triangle sum theorem to find missing angle measurements in a triangle Use the exterior angle theorem to find missing angle measurements in a triangle

What do the angles of a triangle add up to? Why? How can we prove this?

ACTIVITY Cut a triangle. (Any type of triangle, any size) 2. Label the corners of the Triangle A, B, C 3. How can we prove that the sum of all angles add up to 180°?

Triangle sum theorem Triangle Sum Theorem: Angles in a triangle add up to 180°.

1. Find the measure of ∠𝐶.

2. Find the missing angle measurements

3. Find the value of x.

4. Find the measure of angle A

Exterior angle theorem

5. Find 𝑚∠𝐵 6. Find the 𝑚∠𝐶𝐴𝐵

7. Find the 𝑚∠𝑅𝑃𝑄

Objective Use triangle sum theorem to find missing angle measurements in a triangle Use the exterior angle theorem to find missing angle measurements in a triangle