proposition: Lemma invf_div x y: (x / y)^-1 = y /x.
proof: Proof. by rewrite invfM mulrC invrK. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq choice fintype order bigop ssralg) mathcomp(div ssrnum ssrint rat prime path binomial) mathcomp(tuple finset) gaia(fibm)