1. Proving Statements About Angles
Chapter 2 Section 2.6-Part 1
Proving Statements About Angles

2. Warm-Up Find the measure of each angle. A right angle 90°
The complement of 42° 48°
The supplement of 42° °
Two congruent angles that are complementary ° and 45°
Two congruent angles that are supplementary ° and 90°

3. Definitions

4. A
mA = 90° A
mA < 90° A is acute A
90° < mA < 180° A is obtuse

8. Use the diagram to decide whether the statement is true or false
True Vertical Angles 
False: 60, 60, 120, 120
True: Both pairs are linear pairs and = 180

9. Make sketch of the given information label all angles that can be determined
42°
48°
42°
138°

10. Make sketch of the given information label all angles that can be determined
90°
42°
138°
42°
138°

11. Solve for x Vertical Angles are  Linear Pairs are Supplementary
4x – 17 = 2x + 9
2x – 17 = 9
2x = 26
x = 13
Linear Pairs are Supplementary
7x x + 8 = 180
10x + 10 = 180
10x = 170
x = 10

12. Solve for x
Vertical Angles are 
3x – 5 = 79
3x = 84
x = 28

13. 1. Given
2. Def. of Complementary Angles
3. Given
4. Def.  Angles
5. Substitution
6. Substitution
7. Def. of Complementary Angles

14. Write a Two Column Proof
Statements Reasons
1. 2  3
1. Given
2. 1   4  3
2. Vertical Angles are 
3. 1  3
3. Transitive
4. 1  4
4. Transitive