The surface area of a trapezoid is calculated using the equation 1/2(a+b)*h, where "a" and "b" are the parallel sides of the trapezoid, and "h" is the vertical height. For example, if side "a" equals three, side "b" equals five and height "h" equals four, then the area equals 1/2(3+5)*4, or 16.
A trapezoid is a type of two-dimensional shape known as a quadrilateral. As with all quadrilaterals, a trapezoid has four sides. Trapezoids have one set of parallel sides. These sides are known as the bases of the trapezoid, while the two non-parallel sides are called the legs. The vertical height is also known as the altitude. When the legs are equal in length, and the angles from a parallel side are equal, the shape is an isosceles trapezoid.