Answer 1

Let the third side of this triangle be x.

Perimeter of triangle = 30 cm

12 cm + 12 cm + x = 30 cm

x = 6 cm

`s="Perimeter of triangle"/2=30/2=15 cm`

By Heron's formula,

`"Area of triangle "=sqrt(s(s-a)(s-b)(s-c))`

                          `=[sqrt(15(15-12)(15-12)(15-6))]cm^2`

                          `=[sqrt(15(3)(3)(9))]`

                          `=9sqrt15 cm^2`