proposition: Lemma opair_inj1 x x' y y' : M_opair x y = M_opair x' y' -> x = x'.
proof: Proof. Proof using M_ZF VIEQ. intros He. assert (H : {x; x} ∈ M_opair x y) by apply M_pair1. rewrite He in H. apply M_pair in H as [H|H]; apply (sing_pair H). Qed.
imports: Undecidability.FOL(Syntax.Facts Semantics.Tarski.FullFacts) Undecidability.FOL(Sets.ZF) Undecidability.FOL(ZF) Undecidability.FOL.TRAKHTENBROT(hfs) Undecidability.Shared.Libs.DLW.Utils(finite) Undecidability(Shared.ListAutomation) Lia