(* Gabriel Braun April 2013 *)
Require Export GeoCoq.Tarski_dev.Ch13_5_Pappus_Pascal.
Section Desargues_Hessenberg.
Context `{T2D:Tarski_2D}.
Context `{TE:@Tarski_euclidean Tn TnEQD}.

Lemma l13_18_2 : forall A B C A' B' C' O, ~Col A B C
-> Par_strict A B A' B'
-> Par_strict A C A' C'
-> (Par_strict B C B' C' /\ Col O A A' /\ Col O B B' -> Col O C C').