proposition: Lemma agenvEr U : agenv U = (1 + agenv U * U)%VS.
proof: Proof. rewrite [lhs in lhs = _]agenvEl big_distrr big_distrl /=; congr (_ + _)%VS. by apply: eq_bigr => i _ /=; rewrite -expvSr -expvSl. 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)