proposition: Theorem isupport_aux_not_in: forall b l, (forall a, (In a support) -> op b a <> e \/ op a b <> e) -> ~ In b (isupport_aux l).
proof: Proof. intros b l; elim l; simpl; simpl; auto. intros a l1 H; case_eq (is_inv a); intros H1; simpl; auto. intros H2 [H3 | H3]; subst. contradict H1. unfold is_inv; rewrite is_inv_aux_false; auto. case H; auto; apply isupport_aux_is_in; auto. Qed.
imports: ZArith Tactic Wf_nat UList ListAux FGroup