proposition: Theorem Sstar_contains_Rstar : forall (U:Type) (R S:Relation U), contains U (Rstar U S) R -> contains U (Rstar U S) (Rstar U R).
proof: Proof. unfold contains. intros U R S H' x y H'0; elim H'0; auto with sets. generalize Rstar_transitive; intro T1; red in T1. intros x0 y0 z H'1 H'2 H'3; apply T1 with y0; auto with sets. Qed.
imports: Relations_1 Relations_1_facts Relations_2