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Formula for geometrical figures

pi ( π ) = 3.1415926535...

Perimeter formula
Square	4 × side
Rectangle	2 × (length + width)
Parallelogram	2 × (side1 + side2)
Triangle	side1 + side2 + side3
Regular n-polygon	n × side
Trapezoid	height × (base1 + base2) / 2
Trapezoid	base1 + base2 + height × [csc(theta1) + csc(theta2)]
Circle	2 × pi × radius
Ellipse	4 × radius1 × E(k,pi/2)

E(k,pi/2) is the Complete Elliptic Integral of the Second Kind

k = (1/radius1) * sqrt(radius1² - radius2²)

Area formula
Square	side²
Rectangle	length × width
Parallelogram	base × height
Triangle	base * height / 2
Regular n-polygon	(1/4) × n × side² × cot(pi/n)
Trapezoid	height × (base1 + base2) / 2
Circle	pi × radius²
Ellipse	pi × radius1 × radius2
Cube (surface)	6 × side²
Sphere (surface)	4 × pi × radius²
Cylinder (surface)	2 × pi × radius × height
Cone (surface)	pi × radius × side
Torus (surface)	pi² × (radius2² - radius1²)

Volume formulas
Cube	side³
Rectangular Prism	side1 × side2 × side3
Sphere	(4/3) × pi × radius³
Ellipsoid	(4/3) × pi × radius1 × radius2 × radius3
Cylinder	pi × radius² × height
Cone	(1/3) × pi × radius² × height
Pyramid	(1/3) × (base area) × height
Torus	(1/4) × pi² × (r1 + r2) × (r1 - r2)²

Source: Spiegel, Murray R. Mathematical Handbook of Formulas and Tables.

Schaum's Outline series in Mathematics. McGraw-Hill Book Co., 1968.