proposition: Lemma mulRCA x y z : x * (y * z) == y * (x * z).
proof: Proof. by rewrite !mulRA (mulRC x). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div order) mathcomp(ssralg ssrnum ssrint rat intdiv) Coq(Morphisms Setoid) fourcolor(real realsyntax)