Download PPSection 3.2

Geometry: Section 3.2
Parallel Lines and Transversals
What you will learn:
1.Use properties of parallel lines
2. Prove theorems about parallel lines
3. Solve real-life problems
The following two statements were actually
part of Chapter 2, but let’s look at them now.
Postulate 2.8 Linear Pair Postulate
If two angles form a linear pair, then
they are supplementary
Theorem 2.6 Vertical Angles Theorem
If two angles are vertical angles, then
they are congruent
Theorem 3.1
Corresponding Angles Theorem
If two parallel lines are cut by a transversal, then
corresponding angles are congruent
Theorem 3.2 Alternate Interior Angles Theorem
If two parallel line are cut by a transversal, then
alternate interior angles are congruent
1) a || b
) 3  6
1) Given
Theorem 3.3 Alternate Exterior Angles Theorem
If two parallel line are cut by a transversal, then
alternate exterior angles are congruent
Theorem 3.4 Consecutive Interior Angles Theorem
If two parallel line are cut by a transversal, then
consecutive interior angles are supplementary
3 x  5  7 x  11
5  4 x  11
16  4 x
x4
3 y  5  7 y  11  180
10 y  6  180
10 y  186
y  18.6
5w  8  3w  6  180
8w  14  180
8w  166
w  20.75
HW: pp 135 & 136 / 2 – 12, 18, 19