proposition: Lemma intrM m n : (m * n)%:~R = m%:~R * n%:~R :> R.
proof: Proof. by rewrite mulrzA -mulrzr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)