Section T7_2.
Context {Tn:Tarski_neutral_dimensionless}.
Context {TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality Tn}.
(** This is Krippen lemma , proved by Gupta in its PhD in 1965 as Theorem 3.45 *)

Lemma bet2_lt2__lt : forall O o A B a b : Tpoint,
Bet a o b -> Bet A O B -> Lt o a O A -> Lt o b O B -> Lt a b A B.