# Trapezoid

A Trapezoid is a 4-sided polygon (Quadrilateral) which has at least one pair of parallel sides. The sides of a Trapezoid that are parallel are called the bases of the trapezoid and the other two sides are called the legs or the lateral sides. The perpendicular distance from one base to the other is called the altitude of a trapezoid. The line joining the midpoints of the two legs is called as the median or midline or midsegment of a trapezoid.

ABCD is a trapezoid with AB and CD as bases and AD and BC as legs. Perpendicular from B to CD is the altitude or height of the trapezoid. A line joining the midpoints of AD and BC is the median.

The median's length is the average of the two base lengths and is given by,

m = $\frac{b_1 + b_2}{2}$ where $b_1$ and $b_2$ are the lengths of the parallel bases.