Proving Lines Parallel Section 3.2

Remember Postulate 3.1 told us that: If two parallel lines are crossed by a ____________________, then corresponding angles are ______________________. Write the converse of this Postulate: ___________________________________________________________________________ We will prove this theorem true. How will it be useful? 1___________________________________________________________________________ 2. __________________________________________________________________________

Theorem 3.1: If Two Parallel lines are crossed by a transversal, then the alternate interior angles are congruent. Write the converse of This theorem:_________________________________________________________________ _________________________________________________________________________ We will later prove this theorem be true. How could this be useful? 1.________________________________________________________________________ 2. ________________________________________________________________________

WE also learned Theorem 3 WE also learned Theorem 3.2: If two parallel lines are crossed by a transversal, then the same side interior angles are supplementary. Write the converse:_________________________________________________________________ __________________________________________________________________________ We will later prove this converse true. How can it be useful? 1. _______________________________________________________________________ 2. _______________________________________________________________________

Example: Determine the value of x for which A ∥ B, IF M∠1 = 80 –X, AND M∠2 = 90-2X.