proposition: Lemma mulRI x y z : x != 0 -> x * y == x * z -> y == z.
proof: Proof. move=> nz_x /(mulR_Proper (eqR_refl x^-1)). by rewrite -!(mulRCA x) !mulRA divRR ?mul1R. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div order) mathcomp(ssralg ssrnum ssrint rat intdiv) Coq(Morphisms Setoid) fourcolor(real realsyntax)