Area and volume > Area 2-D shapes
1234Area 2-D shapes

Theory

You can find the area of a figure by dividing it into rectangles and half rectangles. This even works to find the (approximate) area of a circle. You know the area of a rectangle: area  ( rectangle ) = height width .

It is handy to memorize the following area formulas:

By moving either point P or point Q parallel with the base the area does not change. This is called Cavalieri's principle.

The circumference of a circle with radius r is: circum  ( circle ) = 2 π r .
The area of a circle with radius r is: area ( circle ) = π r 2 .

previous | next