Area Formulas
Square = a 2 
Rectangle = ab
Parallelogram = bh
Trapezoid = h/2 (b1 + b2)
Circle = pi r 2
Ellipse = pi r1 r2
Rectangle = ab
Parallelogram = bh
Trapezoid = h/2 (b1 + b2)
Circle = pi r 2
Ellipse = pi r1 r2
| triangle = |  |  | one half times the base length times the height of the triangle |
| equilateral triangle = |  |
triangle given SAS (two sides and the opposite angle)= (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)
[s(s-a)(s-b)(s-c)] when s = (a+b+c)/2 (Heron's formula)
regular polygon = (1/2) n sin(360°/n) S2
when n = # of sides and S = length from center to a corner
when n = # of sides and S = length from center to a corner
Area is measured in "square" units. The area of a figure is the number of squares required to cover it completely, like tiles on a floor.
Area of a square = side times side. Since each side of a square is the same, it can simply be the length of one side squared.
If a square has one side of 4 inches, the area would be 4 inches times 4 inches, or 16 square inches. (Square inches can also be written in2.)
Be sure to use the same units for all measurements. You cannot multiply feet times inches, it doesn't make a square measurement.
