## 3.3 Proving Lines Parallel

Converse of Corresponding Angles Postulate: If two coplanar lines are cut by a transversal so that a pair of corresponding angles are congruent, then the two lines are parallel.

Parallel Postulate: Through a point P not on line l, there is exactly one line parallel to l.

Converse of the Alternate Interior Angles Theorem: If two coplanar lines are cut by a transversal so that a pair of alternate interior angles are congruent, then the two lines are parallel.

Converse of the Alternate Exterior Angles Theorem: If two coplanar lines are cut by a transversal so that a pair of alternate exterior angles are congruent, then the two lines are parallel.

Converse of the Same-Side Interior Angles Theorem: If two coplanar lines are cut by a transversal so that a pair of same-side interior angles are csupplementary, then the two lines are parallel.

Parallel Postulate: Through a point P not on line l, there is exactly one line parallel to l.

Converse of the Alternate Interior Angles Theorem: If two coplanar lines are cut by a transversal so that a pair of alternate interior angles are congruent, then the two lines are parallel.

Converse of the Alternate Exterior Angles Theorem: If two coplanar lines are cut by a transversal so that a pair of alternate exterior angles are congruent, then the two lines are parallel.

Converse of the Same-Side Interior Angles Theorem: If two coplanar lines are cut by a transversal so that a pair of same-side interior angles are csupplementary, then the two lines are parallel.