proposition: Lemma ppX : pp 'X %= 'X.
proof: Proof. by rewrite {2}(ppP 'X) -{1}[pp _]mul1r eqd_mul // eqd_sym (polyC_inj_eqd gcdsrX). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(path choice fintype tuple finset ssralg) mathcomp(matrix poly) mathcomp(bigop polydiv) CoqEAL(stronglydiscrete dvdring)