Newbie here, I'm studying the proof of Cauchy's rigidity theorem, but couldn't find any good resources. I read the chapter about it Proofs from THE BOOK, but it's really brief and I was not able to fully understand it. Can someone recommend me some resources or places to search? The main part about creating a spherical polygon from a polyhedron and a sphere is pretty straight forward (once you know about the existence of a required vertex) (I will welcome arguments saying the opposite), but especially the Cauchy's arm lemma and the induction is not so easy to grasp.
Thanks.