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