Part a) :
Let hypotenuse of the lower triangle be h . Then the opposite of
For upper triangle
and opposite to
By the condition of part(b) of the given problem the perimeter of both the triangle (upper and lower) are same. So we can say that the sum of other two sides excluding common side will be same for both the triangles.
Adding (1) and (2) we get
By the given condition of part (a) of the question
Area of the upper triangle = Area of the lower triangle