3.3 Parallel and Perpendicular Lines

To Relate Parallel and Perpendicular Lines

Theorem 3.9

Proof #1

l || k Given

k|| m Given

l || m Transitive Property

Theorem 3-10

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 ||s Converse of Corresponding Angles

Theorem 3-11

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