45° - 45° - 90° => isosceles rigth triangle, the two legs have the same length.
Call a the length of the legs and h the length of the hypotenuse =>
a^2 + a^2 = h^2
=> 2a^2 = h^2
=> a^2 = h^2 / 2
=> a = h / √2 = 22 / √2 = 15.6 units
Answer: 15.6 units