Trapezoid

A trapezoid (in North America) or trapezium (in Britain and elsewhere) is a quadrilateral, which is defined as a shape with four sides. This shape has two parallel sides which are called the bases of the trapezoid, and another two sides called its legs. In North America, the term "trapezium" is used for what is elsewhere called an irregular quadrilateral, which has no parallel sides[1].

Special cases

Some trapezoids are special cases where they have at least one noteworthy feature:

Iscoceles trapezoids: These have legs that are of the same length, and because of that, this trapezoid has a pair of angles of the same wideness (congruent).

Calculating area

To calculate the area of a trapezoid, you must add the two parallel sides together, divide that by 2, then times that by its height.

A={\frac {a+b}{2}}\cdot h

Other websites

"Trapezoid" on MathWorld
Trapezoid definition Area of a trapezoid Median of a trapezoid With interactive animations
Trapezoid (North America) at elsy.at: Animated course (construction, circumference, area)

References

"1913 American definition of trapezium". Merriam-Webster Online Dictionary. Retrieved 2007-12-10.

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[1] "1913 American definition of trapezium". Merriam-Webster Online Dictionary. Retrieved 2007-12-10.