proposition: Lemma andE2 (T : System) (f g : Formula): SysPrf T (f /\ g)%fol -> SysPrf T g.
proof: Proof. intros H; apply nnE. apply impE with (f /\ g)%fol. - apply cp2, impI, orI2, Axm; right; constructor. - assumption. Qed.
imports: Coq(Ensembles List) hydras.Ackermann(ListExt folProof folProp Deduction)