I have read a book called "Proofs From The Book", but it defined many terms and contains much terminology, so I couldn't understand how to obtain a proof by using Bricard's condition. However, I couldn't understand the proof of Bricard's condition either, so I have no hope to understand the formal proof, hope you could give me the intuition behind the proof.
Thanks in advance!
P.S. And how do we define split of tetrahedra?