The area of a triangle is given in terms of the side lengths (b, h) as
... A = (1/2)bh
If b=h, then we can find the side length as ...
... A = (1/2)b²
... b = √(2A) . . . . . multiply by 2 and take the square root
The hypotenuse (x) can be found from the Pythagorean theorem:
... x² = b² + h² = 2b²
... x = b√2
The perimeter is the sum of the side lengths, so is
... P = b + b + x = 2√(2A) + (√(2A))·√2
... P = (2+√2)·√(2A)