Area Formulas

The standard notation for area is A.

Square

Let's a square side is long a then area formula is:

A = a.a = a²

Rectangle

Let's a rectangle sides are long a and b

A = a.b

Parallelogram

Let's palallelogram sides are long a and b and h_a is the altitude to the side a, and h_b is the altitude to the side b
Parallelogram area formula is:

A = a.h_a = b.h_b

Parallelogram area formula explained.(a java applet will be opened in a new window).

Trapezoid

Say the length of the parallel sides of a trapezoid are long a and b and the distance between the two bases is h(the trapezoid altitude). The area formula is:

A = ½(a + b)h

Triangle

ABC is triangle

the length of the sides is: a, b, c and the length of the altitudes is: h_a, h_b and h_c.

A = ½(a.h_a) = ½(b.h_b) = ½(c.h_c)
A = ½(ab.sinC) = ½(ac.sinB) = ½(bc.sinA)

p = ½(a + b + c)

A = √p(p - a)(p - b)(p - c) - Heron formula

A = R²sinA.sinB.sinC = ^abc/_4R

Circle area formulas.

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