Question

Find the length of a leg

Answer 1

2 corners are both 45 degrees, meaning that they are both the same length.

For this we use the pythagorean theorem, but a bit modified:
a^2 + a^2 = c^2
2a^2 = 256

Solve for a:
a^2 = 128
a = 8 √2

One leg is equal to √128 or 8 √2.