proposition: Lemma mulA : associative mul.
proof: Proof. elim/quotW=> x; elim/quotW=> y; elim/quotW=> z; rewrite !piE. by rewrite /mulf !numden_Ratio ?mulf_neq0 ?domP // !mulrA. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(ssrAC choice tuple bigop ssralg poly polydiv) mathcomp(generic_quotient)