trapezium (trapezia)

A trapezium is an irregular quadrilateral with four vertices and four sides.

It has one pair of parallel sides. The other two sides are not parallel (if they were parallel the trapezium would be a parallelogram).

A trapezium doesn’t usually have lines of symmetry, except for an isosceles trapezium which has one line of symmetry.

The formula for the area of a trapezium is:

(1)   \begin{align*} \text{Area} &= \frac{\text{1}}{\text{2}}\times(a + b) \times h \\ \textmd{A} &= \frac{\textmd{(a + b)}}{\textmd{2}}\ h \end{align*}

In this formula a and b refer to the length of the parallel sides, and h refers to the height of the trapezium, i.e. the perpendicular distance between the parallel sides a and b.