proposition: Lemma prop_4 : forall A B C D E F, CongA C A B F D E -> Cong A C D F -> Cong A B D E -> Cong C B F E /\ (C <> B -> CongA A C B D F E /\ CongA A B C D E F).
proof: Proof. intros A B C D E F. apply l11_49. Qed.
imports: GeoCoq.Meta_theory.Continuity.elementary_continuity_props GeoCoq.Tarski_dev.Ch16_coordinates_with_functions