proposition: Lemma BRprod_eq2l x y z: realp x -> realp y -> realp z -> z <> \0r -> z *r x = z *r y -> x = y.
proof: Proof. rewrite (BRprodC z) (BRprodC z); apply: BRprod_eq2r. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)