proposition: Lemma F_not_in_G x E: ~ F x ∈ Gs E.
proof: Proof. intros (a & b & c & []) % in_Gs. eapply disjoint_F_G; eauto. Qed.
imports: RelationClasses Morphisms List Lia Init.Nat Setoid Undecidability.HOU(calculus.calculus second_order.diophantine_equations systemunification nth_order_unification)