A trapezoid is a quadrilateral whose two sides are parallel. In the figure below, is a trapezoid and is parallel to . In this post, we are going to prove that in a trapezoid, the consecutive angles between a pair of parallel sides are complementary. That is, we are going to prove in the figure above that degrees and .

**The Trapezoid Angle Theorem.**

In a trapezoid, the consecutive angles between a pair of parallel sides are complementary. Continue reading…