Section T15.
Context `{T2D:Tarski_2D}.
Context `{TE:@Tarski_euclidean Tn TnEQD}.
(** Lemma 15.2 *)
(** Cong corresponds to length equality.*)
(** Le corresponds to length inequality.*)

Lemma leP_bet : forall O E E' AB CD,
LeP O E E' AB CD -> LeP O E E' O AB -> LeP O E E' O CD -> Bet O AB CD.