Alternative Proofs To Euclid's Propositions

[moe darklight]

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?

 

[fresh_42]

I can only recommend https://www.amazon.com/dp/0486600882/?tag=pfamazon01-20 and the following volumes. If your theorem has a name, then it is very likely that many proofs can be found using that name on an internet search. But if it is just a theorem - number 37 - then it will be difficult to find it.

 

[DaTario]

This edition has all thirteen books in one volume.
https://www.amazon.com/dp/1888009195/?tag=pfamazon01-20

Besides, it appeared in Numberphile episode on prime numbers: