proposition: Lemma eqp_size p q : p %= q -> size p = size q.
proof: Proof. have [->|Eq] := eqVneq q 0; first by rewrite eqp0; move/eqP->. rewrite eqp_sym; have [->|Ep] := eqVneq p 0; first by rewrite eqp0; move/eqP->. by case/andP => Dp Dq; apply: anti_leq; rewrite !dvdp_leq. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop ssralg poly)