## Trigonometry (10th Edition)

The length of the diagonal is $L = \sqrt{2}~k$
We can use the Pythagorean theorem to find the length $L$ of the diagonal: $L^2 = k^2+k^2$ $L = \sqrt{k^2+k^2}$ $L = \sqrt{2k^2}$ $L = \sqrt{2}~k$