proposition: Lemma Ratio_numden : forall x, Ratio \n_x \d_x = x.
proof: Proof. case=> [[n d] /= nd]; rewrite /Ratio /insubd; apply: val_inj=> /=. by case: insubP=> //=; rewrite nd. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(ssrAC choice tuple bigop ssralg poly polydiv) mathcomp(generic_quotient)