1. Angles of Triangles

2. Angles
Interior angles
Exterior angles

3. 4.1: Triangle Sum Theorem

4. Examples triangle sum theorem

5. 4.2 Exterior Angle Theorem
Remote Interior Angles 2
Exterior Angle 3 1

6. Examples Exterior angle theorem

7. 3 4. 4

8. Ex 5: Find the measure of each numbered angle in the figure below.65 82 46 1 5
142 2 4 3

9. Example 6 Find x and the x
2x + 21

10. Example 7 Find x and the 2x x
X - 20

11. Example 8 Find x and the 80
3x - 22 x

12. Example 9: Find the 80
3x +6 x

13. Third Angle Sum Theorem
If two angles of a triangle are congruent to two angles of a second triangle, then the third angles of the triangles are congruent.

14. Corollaries
4.1 : The acute angles of a right triangle are complementary. 4.2 : There can be at most one right or obtuse angle in a triangle.

15. 10
11.