Answer:
3sqrt2
Step-by-step explanation:
If a side length is a, then a^2 + a^2 = 36
2a^2 = 36
a^2 = 18
a = 3sqrt2
Or, you can remember that in a square, if you cut it in half diagonally, you get a 45-45-90 triangle, so the sidenglth is diagonal/sqrt2
