proposition: Lemma prop_3 : forall A B C1 C2, Le C1 C2 A B -> exists E, Bet A E B /\ Cong C1 C2 A E.
proof: Proof. auto. Qed.
imports: GeoCoq.Meta_theory.Continuity.elementary_continuity_props GeoCoq.Tarski_dev.Ch16_coordinates_with_functions