So lately I've been trying to start practicing proving things without being given a prompt (as in actually finding something out, not answering the question: "prove so and so"), which I'd never done before. -- But then the bummer is not knowing the name of what you've just proved So after searching I found out that one is a proof of Euclid's proposition 37 from book I (Triangles which are on the same base and in the same parallels equal one another). -- Is there a website where I can find alternative proofs from the one given in the actual book? I used an algebraic proof and I want to find out who came up with it. -- I found websites with a bazillion (ok, more like 3 or 4) alternative proofs to the pythagorean theorem, but I can't find a website with proofs to the other propositions. Is there like a proofs directory somewhere out there or something?