Section 3-3Parallel Lines and

Transversals

Properties of Parallel Lines

Corresponding angles postulate

• If two parallel lines are cut by a transversal, then the pairs of corresponding angles are congruent.

Example:1

2

21

Alternate interior angles Theorem

• If two parallel lines are cut by a transversal, then the pairs of alternate interior angle are congruent.

Example:

34

43

consecutive interior angles Theorem

• If two parallel lines are cut by a transversal, then the pairs of consecutive interior angle are supplementary.

Example:

56

18065 mm

Alternate Exterior angles Theorem

• If two parallel lines are cut by a transversal, then the pairs of alternate exterior angle are congruent.

Example:7

8

87

Perpendicular transversal Theorem

• If a transversal is perpendicular to one of two parallel lines, then it is perpendicular to the other.

Example:

a

b

l

al bl therefore