Trapezoid

A trapezoid is a four-sided polygon with two parallel sides.

The following properties arise from the definition:

• Two of the pairs of adjacent angles sum to 180^o
• The area is the mean of the parallel sides multiplied by the distance between them.
• The perimeter is equal to the sum of the oblique sides plus the sum of the tangent sides.
• The sum of the oblique angles will be equal to the sum of the tangent angles.

In England, such a shape is called a trapezium.