Finish proving I.29:

A. If two lines are parallel, then the two interior angles on the same side of a transversal line are supplementary (add up to 2 right angles)

B. If two lines are parallel, then the alternate exterior angles with a transversal line are congruent

C. If two lines are parallel, then the corresponding angles are congruent

Finish proving I.32: An exterior angle to a triangle is equal to the sum of the opposite interior angles of the triangle.