proposition: Lemma binunion_eset x : x = ∅ ∪ x.
proof: Proof. Proof using VIEQ M_ZF. apply M_ext. - intros y H. apply binunion_el. now right. - intros y [H|H] % binunion_el. + now apply M_eset in H. + assumption. 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)