Use the Pythagorean Theorem:
a^2 = b^2 = c^2
c = diagonal/hypotenuse
A rectangle with a length of 32 untis and a width of 18 units; find the length of a diagonal.
2 answers
Or, for those of us with a "+" key,
a^2 + b^2 = c^2
:-)
a^2 + b^2 = c^2
:-)