proposition: Lemma BetS_BetS : forall A B C, Definitions.BetS A B C <-> BetS A B C.
proof: Proof. intros. unfold BetS;simpl. intuition. Qed.
imports: GeoCoq.Tarski_dev.Ch12_parallel GeoCoq.Axioms.euclidean_axioms GeoCoq.Axioms.continuity_axioms GeoCoq.Meta_theory.Continuity.elementary_continuity_props GeoCoq.Meta_theory.Parallel_postulates.parallel_postulates