proposition: Lemma M_pair x y z : x ∈ {y; z} <-> x = y \/ x = z.
proof: Proof. Proof using VIEQ M_ZF. rewrite <- !VIEQ. apply (@M_ZF (fun _ => ∅) ax_pair). cbn; tauto. Qed.
imports: Undecidability.FOL(Syntax.Facts Semantics.Tarski.FullFacts ZF) Undecidability.FOL.Sets(ZF binZF) Undecidability.FOL.Sets.Models(Aczel Aczel_CE Aczel_TD) Coq(Lia)