GM-U2.2 Lesson: Proving Lines Parallel

Unit 2 Lesson 2a:
Proving Lines Parallel

​Goal:

Students are going to use angle relationships to prove lines parallel, and solve problems of proving lines parallel.

Procedure:

1) Identify corresponding, alternate interior, or alternate exterior angles that the parallel lines share.
2) If any of those angles are congruent, the lines are parallel.
or
3) Identify same side interior or exterior angles.
4) If those angles are supplementary, the lines are parallel.

example 1:

example 2:

Are the lines parallel?

How do you know?

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example 3: