proposition: Lemma eqp_gcd p1 p2 q1 q2 : p1 %= p2 -> q1 %= q2 -> gcdp p1 q1 %= gcdp p2 q2.
proof: Proof. move=> e1 e2; exact: eqp_trans (eqp_gcdr _ e2) (eqp_gcdl _ e1). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop ssralg poly)