In a 45-45-90 degrees triangle, the two shorter sides are congruent, and the hypotenuse is √2 times the length of either shorter side.
If the shorter sides are each 4/5, then the hypotenuse would be:
hypotenuse = √2 * (4/5) = (4√2)/5
So, the remaining side of the triangle is (4√2)/5, which is the same length as the hypotenuse.