# 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 = a

^{2}#### 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

#### Area calculator

**Enter the triangle:**

#### Area of a right triangle

$S=\frac{a.b}{2}$

$S=\frac{c.h_c}{2}$

#### Triangle

ABC is a 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(ab.sinC) = ½(ac.sinB) = ½(bc.sinA)

p = ½(a + b + c)
_{a}) = ½(b.h_{b}) = ½(c.h_{c})A = ½(ab.sinC) = ½(ac.sinB) = ½(bc.sinA)

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

A = R

^{2}sinA.sinB.sinC =^{abc}/_{4R}