proposition: Lemma ler_pV2 : {in [pred x in GRing.unit | 0 < x] &, {mono (@GRing.inv R) : x y /~ x <= y}}.
proof: Proof. move=> x y /andP [ux hx] /andP [uy hy] /=. by rewrite -(ler_pM2l hx) -(ler_pM2r hy) !(divrr, mulrVK) ?unitf_gt0 // mul1r. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)