Find the area of an isosceles triangle, whose equal sides are of length 15 cm each and third side is 12 cm.
Area of isosceles triangle = 12/4 root under(4 x 15^{2 }- 12^{2}) = 12/4 root under (√900 - 144)
= 3√756 = 3 x 6√21 = 18√21 cm^{2}