Maths Times Infinity > Topics > Area

Area

Rectangle

A=wh

The area of a rectangle is its width times its height.

Triangle

A=(1/2)bh

The area of a triangle is half the product of its base with its perpendicular height.

If you cut a rectangle in half, you get a triangle with half the area of the rectangle. In fact, this applies to all rectangles and triangles with the same dimensions (base and height) except that pieces have to be rearranged.

Circle

A=πr²

The area of a circle is pi time its radius squared.

Trapezium

Another way of writing it:

(y-y₁)/(x-x₁)=m.

The gradient is m so for any point on the line (x,y), the rise/run ratio from (x₁,y₁) to (x,y) should be m.

Line - Two Points

(y-y₁)/(x-x₁)=(y₂-y₁)/(x₂-x₁).

Same as Point and Gradient except first we calculate the gradient using the two points, then use either point as a kind of pivot.