Find the area of an isosceles triangle whose equal sides are of length 15 cm each and third side is 12 cm.

The correct answer is: 18√21 cm2

It is given that a = 15 cm , b = 15 cm , c = 12 cm
Using Heron’s formula,
Area of triangle =  where s = 
s =  = 21
Area of triangle = 
= 
= 
So, area of isosceles triangle = 
NOTE – We can use direct formula of area of isosceles triangle =  where a is an equal side and b is base of triangle
a = 15 cm , b = 12 cm
Area of isosceles triangle = 
= 
= 6