proposition: Lemma binunion_eset x : x = ∅ ∪ x.
proof: Proof. Proof using M_ZF VIEQ. 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) Undecidability.FOL(Sets.ZF) Undecidability.FOL(ZF) Undecidability.FOL.TRAKHTENBROT(hfs) Undecidability.Shared.Libs.DLW.Utils(finite) Undecidability(Shared.ListAutomation) Lia