Need help with the area of an isosceles triangle?

hmm
x = the length of the sides of the same length
y = length of the other side

(y/2) (square root(x^2 - (y/2)^2))

the (square root(x^2 - (y/2)^2)) is the height of the triangle and y is the base and 1/2 is from the formula area = (1/2)*base*height for a triangle

If given only the value for the total perimeter, the area cannot be determined.

If the value of each side is known, A = √[s*(s-a)*(s-b)*(s-c)] where s = (a+b+c)/2

Are you given the lengths of the sides?