proposition: Lemma ppC : forall c, c != 0 -> pp c%:P %= 1.
proof: Proof. move=> c c0. move: (eqd_trans (polyC_inj_eqd (gcdsrC c)) (eq_eqd (ppP c%:P))). rewrite -{1}[(gcdsr c%:P)%:P]mulr1. have g0: (gcdsr c%:P)%:P != 0. by rewrite polyC_eq0 gcdsr_eq0 polyC_eq0. by rewrite eqd_mul2l// eqd_sym. 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)