Let's say there is a big square with side length l and vertices X, B, C, D. A line AE cuts it to form pentagon ABCDE. Now if I draw a smaller square inside of this pentagon so that 2 of its vertices are on side AE of the pentagon and the other 2 are on BC and CD, am I right in using AB (a) and DE (b) to conclude that AE (s) must be sqrt(a^2 + b^2) using the Pythagorean theorem?