Find the area of a triangle two sides of which are 18 cm and 10 cm and the perimeter is 42 cm.
Let the third side of the triangle is 
Since the perimeter of a triangle is given by:
cm
Let a, b and c are the sides of triangle and s is the semi-perimeter, then its area is given by:
A = 
where 
[Heron’s Formula]
= 
= 21
A = 
A = 
= 
cm2
4