Pythagoras, Pythagorean, Euclidean, Gravitational Lensing, Symmetry.
rectangle triangle. Symmetry. Watching this mesmerizing Figure 4 doesn’t help, still, the true reason behind c² = a² + b² seems to escape our understanding. To help on this issue, we have to ask further. What are the conditions hidden in Figure 1 or 4, that allows us to advance in our conclusions