(* 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 l13_8 : forall O P Q U V, U <> O -> V <> O -> Col O P Q -> Col O U V
-> Per P U O -> Per Q V O -> (Out O P Q <-> Out O U V).