proposition: Lemma mul1_l : left_id 1%:F mul.
proof: Proof. elim/quotW=> x; rewrite !piE /mulf. by rewrite !numden_Ratio ?oner_eq0 // !mul1r Ratio_numden. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(ssrAC choice tuple bigop ssralg poly polydiv) mathcomp(generic_quotient)