Midline of a trapezium

Given a trapezium $ABCD$ with $AB$ and $CD$ as the parallel sides, let $E$ and $F$ be the midpoints of the non-parallel sides $AD$ and $BC$, respectively. The segment $EF$ is called the midline (or median) of the trapezium.

Important properties

• The midline $EF$ is parallel to the bases $AB$ and $CD$.

• The length of the midline is the average of the lengths of the two bases: $EF = \frac{AB + CD}{2}$