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

Lemma per3_preserves_bet2 : forall O A B C A' B' C', Col O A C -> A' <> C' ->
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' C' -> Bet A B C.