Pythagoras, Pythagorean, Euclidean, Gravitational Lensing, Symmetry.
like (meters, inches, etc.) as long as the units are the same for the 3 sides, of course. Usually, this equation is taught as something given (by Gods?) and students just memorize it and later forget. Instead, if you ask first why, and later find an explanation, I bet you will never forget. Making