find area of isoceles triangle whose base is 'a' and equal sides of  length 'b' 

let first side be a
     second side be b
  and third side also b as it is an isosceles triangle

s=a+b+b 
         2
=a+2b
​      2

AREA=root s(s- a)(s-b)(s-b)
           =root a+2b(a+2b-a)(a+2b-b)(a+2b-b)​
                        2         2          2           2

It is not required to simplify it further in 9th class . my teacher had said it. But I'm not sure that in other schools these many steps would be enough
But u can simplify this expression further to get a complicated answer

I'm sorry if I have done any mistake in the answer