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Thanks to @mathfusi for making me aware of Thales's theorem in a comment on the Pythagorean theorem project. I hadn't heard about it before :) Thales's theorem states that if you have a triangle in which the corners are distinct points on a circle, and one of the sides is the diameter of the circle, it is a right triangle. Learn more here: https://en.wikipedia.org/wiki/Thales%27s_theorem
