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(* Formalization of the Chou, Gao and Zhang's decision procedure.          *)
(* Julien Narboux (Julien@narboux.fr)                                      *)
(* LIX/INRIA FUTURS 2004-2006                                              *)
(* University of Strasbourg 2008                                           *)
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Theorem Pascal :
forall A B C A' B' C' : Point, A<>C' ->
on_line C A B ->
on_parallel B' A B A' ->
on_inter_line_parallel C' A A' B' C A' ->
parallel B C' B' C.