The easy fudge factor for this is 1.4 for half square triangles. If you divide the length of the diagonal, 38, by 1.4, you get 27.14. This works because the square root of 2 is 1.4142135, which you could use to be totally accurate. If your right-angle triangle has two equal sides measuring 1 inch, the diagonal will be the square root of 1 squared plus 1 squared, which is 2. The square root of 2 is 1.4142135. The diagonal will always be 1.4142135 times the length of the side. If you want to find the length of the diagonal, MULTIPLY the length of the side by 1.4 and round up a bit. Works for me.