Trapezoid

A trapezoid is a 4-sided flat shape with straight sides that has a pair of opposite sides parallel.


Trapezoid	Isosceles Trapezoid

	A pair of parallel sides
	Called an Isosceles trapezoid when the sides that aren't parallel are equal in length and both angles coming from a parallel side are equal.
	Called a "Trapezium" in the UK

Play with a trapezoid:

The parallel sides are the "bases"

The other two sides are the "legs"

The distance (at right angles) from one base to the other is called the "altitude"

Area of a Trapezoid

The Area is the average of the two base lengths times the altitude:

Area = (6 m + 4 m)/2 × 3 m = 5 m × 3 m = 15 m²

If you can draw your Trapezoid, try the Area of Polygon by Drawing tool.)

The Perimeter is the distance around the edges.

The Perimeter is the sum of all side lengths:

Perimeter = a+b+c+d

Perimeter = 5 cm + 12 cm + 4 cm + 15 cm = 36 cm

The median (also called a midline or midsegment) is a line segment half-way between the two bases.

The median's length is the average of the two base lengths:	m =	a+b

		2

You can calculate the area when you know the median, it is just the median times the height:

Area = mh

A trapezium (UK: trapezoid) is a quadrilateral with NO parallel sides.

The US and UK have their definitions swapped over, like this: