**Overview**

A trapezoid is a quadrilateral with exactly one pair of parallel sides (definitions may differ in other sources). The parallel sides are the **base** and the non parallel sides are called the **legs**. An isosceles trapezoid is a trapezoid whose base are congruent.

In this post, we prove that if a trapezoid is isosceles, its base angles are congruent. In trapezoid ABCD below, $latex \overline{BC} \parallel \overline{AD}$ and $latex \overline{AB} \cong \overline{CD}$. Continue reading