proposition: Lemma rectC_mulr x y z : (x + 'i * y) * z = x * z + 'i * (y * z).
proof: Proof. by rewrite mulrDl mulrA. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)