(* Gabriel Braun April 2013 *)
Require Export GeoCoq.Tarski_dev.Ch12_parallel.
Section L13_1.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
(** Pappus Desargues *)

Lemma per13_preserves_bet_inv : forall A B C A' C', Bet A' B C' -> B <> A' -> B <> C' ->  Col A B C  -> Per B A' A -> Per B C' C -> Bet A B C.