Section T6_2.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
(* Lemma t2_8 : forall A B C D E : Tpoint, Bet A B C -> Bet D B E -> Cong A B D B -> Cong B C B E -> Cong A E C D. *)

Lemma cong_preserves_bet : forall B A' A0 E D' D0,
Bet B A' A0 -> Cong B A' E D' -> Cong B A0 E D0 -> Out E D' D0 ->
Bet E D' D0.