1. Angle Relationships Lesson 9-3

2. Angle Relationships Vertical angles are the opposite angles formed by intersecting lines. Vertical angles are congruent angles, or angles with the same measure. x°x° 40°

3. Find the value of x in the figure. The angle labeled x° and the angle labeled 40° are vertical angles. Therefore, they are congruent. So, the value of x is 40°. x°x° 40°

4. Two angles are complementary if the sum of their measures is 90°. Angle A and angle B are complementary. B= 55° A = 35° A B

5. Two angles are supplementary if the sum of their measures is 180° 130° + 50° = 180° The angles are supplementary

6. Use angle relationships to solve problems. Find the value of x in the figure at the right. Since the angles form a right angle, they are complementary. x° + 25° = 90° (Definition of complementary angles) 65° + 25° = 90° (THINK: What measure added to 25° equals 90°?) So, the value of x is 65.

7. Classify each pair of angles as complementary, supplementary, or neither.

8. Find the value of x in each figure