proposition: Lemma existE (T : System) (f g : Formula) (v : nat): ~ In_freeVarSys LNT v T -> ~ In v (freeVarF g) -> SysPrf T (exH v, f)%nt -> SysPrf T (f -> g)%nt -> SysPrf T g.
proof: Proof. apply (existE LNT). Qed.
imports: Coq(Arith Ensembles List) hydras.Ackermann(Languages folProof folProp folLogic3)