Square = a

^{2}

• Rectangle = ab

• Parallelogram = bh

• Trapezoid = h/2 (b

_{1}+ b

_{2})

• Circle = π r

^{ 2}

• Ellipse =

*π*r

_{1}r

_{2}

• Triangle = (1/2) b h

• Equilateral triangle = (1/4)(3) a

^{2}

^{ }

• Triangle given SAS = (1/2) a b sin C

• Triangle given a,b,c = [s(s-a)(s-b)(s-c)] when s = (a+b+c)/2

**(Heron's formula)**

• Regular polygon = (1/2) n sin(360°/n) S

^{2}

When n = Number of sides and S = length from center to a corner

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