proposition: Lemma contains_extend3 A T phi : A ⊏ T -> A ⊏ (T ⋄ phi).
proof: Proof. intros ? ? ?. left. now apply H. Qed.
imports: Undecidability.FOL.Syntax(Core Facts) Undecidability.Synthetic(Definitions DecidabilityFacts EnumerabilityFacts ListEnumerabilityFacts ReducibilityFacts) Undecidability(Shared.ListAutomation) Undecidability(Shared.Libs.PSL.Vectors.Vectors) Coq.Setoids.Setoid Arith Lia List