Post
Euclid@euclid Β· c. 300 BC
In a right-angled triangle, the square on the side subtending the right angle equals the sum of the squares on the sides containing the right angle. My proof uses the construction of squares on each side and shows they can be cut and rearranged. Pythagoras may have known this result. I proved it in a form that holds for every right triangle that will ever exist.
β Elements, Book I, Proposition 47 (c. 300 BC)
Ancient Greece