proposition: Lemma demo_introv_1 : forall a b, P1 a -> P2 b -> forall c d, P3 c -> P1 d -> c = b.
proof: Proof. Proof using. dup 4. introv. introv. demo. introv A. introv B. introv. intros C D. demo. introv A B. introv. demo. introv A B C D. demo. Qed.
imports: TLC(LibTactics) Coq.micromega.Lia