1. 3.4 Proving that Lines are Parallel
Objectives:
-Identify and use the converse of the Corresponding Angles Postulate.
-Prove that lines are parallel by using theorems and postulates..
Warm-Up: Identify each angle.

6. Write the converse of the "Corresponding Angles Postulate."
Postulate: If two lines cut by a transversal are parallel, then corresponding angles are congruent.

7. Theorem:
Converse of the Corresponding Angles Postulate
If two lines are cut by a transversal in such a way that corresponding angles are congruent, then the two lines are parallel.
Converse of the Corresponding Angles Postulate: If corresponding angles are congruent, then the lines are parallel.

8. Converse of the Same Side Interior Angles Theorem
If two lines are cut by a transversal in such a way that same side interior angles are supplementary, then the two lines are parallel.
Theorem: Converse of the Same-Side Interior Angles Theorem: If same-side interior angles are supplementary, then the lines are parallel.

9. Converse of the Alternate Interior Angles Theorem
If two lines are cut by a transversal in such a way that alternate interior angles are congruent, then the two lines are parallel.
Theorem: Converse of the Alternate Interior Angles Theorem: If alternate interior angles are congruent, then the lines are parallel.

10. Converse of the Alternate Exterior Angles Theorem
If two lines are cut by a transversal in such a way that alternate exterior angles are congruent, then the two lines are parallel.
Theorem: Converse of the Alternate Exterior Angles Theorem: If alternate exterior angles are congruent, then the lines are parallel.

11. Theorem:
If two coplanar lines are perpendicular to the same line, then the two lines are parallel to each other.

12. Theorem:
If two coplanar lines are parallel to the same line, then the two lines are parallel to each other.

13. Are lines m & n parallel? Why or why not?

14. If m<1 = m<7, then 1 || 2 by the Converse of