Section L13_1.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
(** Pappus Desargues *)

Lemma per3_preserves_bet1 : forall O A B C A' B' C', Col O A B -> Bet A B C -> O <> A' -> O <> B' -> O <> C'
-> Per O A' A -> Per O B' B -> Per O C' C
-> Col A' B' C' -> Col O A' B' -> Bet A' B' C'.