proposition: Lemma l11_31_2 : forall A B C D E F, A <> B -> C <> B -> D <> E -> F <> E -> Bet D E F -> LeA A B C D E F.
proof: Proof. intros; destruct (angle_construction_3 A B C D E) as [P HCongA]; auto. exists P; split; try apply in_angle_line; unfold CongA in *; spliter; auto. Qed.
imports: GeoCoq.Tarski_dev.Ch10_line_reflexivity_2