proposition: Lemma binunionr a x y : a ∈ y -> a ∈ x ∪ y.
proof: Proof. Proof using VIEQ M_ZF. intros H. apply binunion_el. now right. 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)