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 image_preserves_bet1 : forall X Y A B C A' B' C',
Bet A B C -> Reflect A A' X Y -> Reflect B B' X Y -> Reflect C C' X Y ->
Bet A' B' C'.