proposition: Lemma conga_os__out : forall A B C C', CongA A B C A B C' -> OS A B C C' -> Out B C C'.
proof: Proof. intros. destruct (conga_cop__or_out_ts A B C C'); trivial. Cop. exfalso; eapply l9_9; eassumption. Qed.
imports: GeoCoq.Tarski_dev.Ch10_line_reflexivity_2