input: Write a python function to calculate the hypotenuse of a right triangle given the lengths of the other two sides.
  assert hypotenuse(3, 4) == 5
  assert hypotenuse(5, 12) == 13
  assert hypotenuse(8, 15) == 17
output: def hypotenuse(a, b):
      return (a**2 + b**2)**0.5