Israel Science and Technology Directory

Formula for geometrical figures

pi (π)=3.1415926535 ...

Perimeter (P) formula
ShapeFormula
CircleP= 2 × pi × radius
SquareP= 4 × side
RectangleP= 2 × (length + width)
ParallelogramP = 2 × (side1 + side2)
TriangleP= side1 + side2 + side3
Regular n-polygonP= n × side
TrapezoidP= base1 + base2 + side1 +side2
Ellipse4 × radius1 × E(k,pi/2)
E(k,pi/2) is the complete elliptic integral of the second kind
k = (1/radius1) × sqrt(radius12 - radius22)

Source: Spiegel, Murray R. Mathematical Handbook of Formulas and Tables.
Schaum's Outline series in Mathematics. McGraw-Hill Book Co., 1968.