If the three lengths of the sides of a triangle are known, Heron's formula can be used to find its area. If a, b, and c are the three lengths of the sides, Heron's formula for area is:
A =

where s is half the perimeter of the triangle, or s =

(a + b + c).
Use this formula to find the area of the triangle if a = 9 cm, b = 11 cm and c = 16 cm.

◦ 180

sq cm
◦ 18

sq cm
◦ 3

sq cm
◦ 18

sq cm