proposition: Lemma subX_agenv U n : (U ^+ n <= agenv U)%VS.
proof: Proof. by case: n => [|n]; rewrite ?sub1_agenv // -(agenvX n) expvS // sub_agenv. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype div tuple finfun bigop ssralg) mathcomp(finalg zmodp matrix vector poly)