Circular area: π (pronounced "pi", also known as "pi", is about 3. 14. ) times the radius of the square.

Circumference: π times diameter.

Square (rectangle) area: side length times side length. Length times width.

Square (rectangle) perimeter: side length multiplied by 4. The sum of the long widening is multiplied by 2.

Annular area: π times the square of the radius of the big circle minus the square of the radius of the small circle.

Area of triangle: base times height divided by 2.

Trapezoidal area: the sum of the upper bottom and the lower bottom multiplied by 2.