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

2. 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

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

4. 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°?

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

6. 1. Find the measure of ∠𝐶.

7. 2. Find the missing angle measurements

8. 3. Find the value of x.

9. 4. Find the measure of angle A

10. Exterior angle theorem

11. 5. Find 𝑚∠𝐵
6. Find the 𝑚∠𝐶𝐴𝐵

12. 7. Find the 𝑚∠𝑅𝑃𝑄

13. 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