proposition: Fact bt_cup_mono s s' t t' : s ⊆ s' -> t ⊆ t' -> s ∪ t ⊆ s' ∪ t'.
proof: Proof. intros H1 H2 x; do 2 rewrite bt_cup_spec. intros [ H | H ]; [ left | right ]; revert H; auto. Qed.
imports: List Arith Lia Max Wellfounded Setoid Eqdep_dec Undecidability.Shared.Libs.DLW.Utils(utils_tac utils_list utils_decidable finite seteq) Undecidability.Shared.Libs.DLW.Vec(pos) Undecidability.Shared.Libs.DLW.Wf(wf_finite wf_chains) Undecidability.FOL.TRAKHTENBROT(notations fol_ops)