1. 3.3 Parallel and Perpendicular Lines To Relate Parallel and Perpendicular Lines

2. Theorem 3.9

3. Proof #1 l || k Given k|| m Given l || m Transitive Property

4. Theorem 3-10

5. Proof #2 r is perpendicular to t Given s is perpendicular to t Given m<1 = m< 2 = 90 Definition of Perpendicular Lines <1 ≅ < 2 Definition of Congruent Angles r ||sConverse of Corresponding Angles

6. Theorem 3-11

7. Proof #3 a is perp. to b Given b||c Given m<1 = 90 Definition of Perpendicular Lines <1 ≅ <2 Corresponding Angles m<2 = 90 Definition of Congruent Angles (Equal Measures) a is perp. to c Definition of Perpendicular Lines