proposition: Lemma l11_14 : forall A B C A' C', Bet A B A' -> A <> B -> A' <> B -> Bet C B C' -> B <> C -> B <> C' -> CongA A B C A' B C'.
proof: Proof. intros. assert_diffs. assert (CongA A' B C C' B A). { apply l11_13 with A C; Between. apply conga_pseudo_refl; auto. } apply l11_13 with A' A; Between. apply conga_right_comm; assumption. Qed.
imports: GeoCoq.Tarski_dev.Ch10_line_reflexivity_2