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