proposition: Fact bt_cup_incl s t x : s ∪ t ⊆ x <-> s ⊆ x /\ t ⊆ x.
proof: Proof. split. + intros H; split; apply bti_trans with (2 := H); auto. + intros [] z; rewrite bt_cup_spec; intros []; 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)