Undo operation and explain why it works adding 28 and dividing by 17

We are given the measurement of the side of a square equal to 16 inches. The square when divided into two using a diagonal forms a 45-45-90 angle. This means this follows the Pythagorean theorem in which the diagonal is square root of 2 times the length of the sides of the square. In this case, the diagonal measures then 16sqrt2 inches