Proof with Tarski.
unfold le.
intros.
intuition.
DecompExAnd H0 Y.
assert (exists B' : Point, Bet C' B' D' /\ Cong_3 C Y D C' B' D').
eapply l4_5;eauto.
DecompExAnd H0 Z.
exists Z.
intuition.
unfold Cong_3 in H6;intuition.
eTarski.
Qed.

Lemma le_reflexivity : forall A B, le A B A B.
Proof with Tarski.