Area of Squares and Rectangles: LxW

Area of a Triangle: bh/2

Perimeter of Polygons: s+s+s+s

Circumference is the perimeter of a circle

Radius is the length from the end of the circle to the middle point.

Diameter is the length from one end of the circle to the other.

Circumference: 2 π r

Area of a circle: π r^2

For area, we always square it.