proposition: Lemma sub_adjoin1v x E : (<<1; x>> <= E)%VS = (x \in E)%VS.
proof: Proof. by rewrite (sameP FadjoinP andP) sub1v. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq div) mathcomp(choice fintype tuple finfun bigop ssralg countalg) mathcomp(finalg zmodp matrix vector falgebra poly polydiv) mathcomp(mxpoly generic_quotient)