**3.3 : Proving Lines Parallel**

**Theorems and Postulates:**

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

Converse of the Corresponding Angles Postulate

**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 the 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 the 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 the same-side interior angles are supplementary, then the two lines are parallel.

**Examples:**