(***************************************************************************)
(* Formalization of the Chou, Gao and Zhang's decision procedure.          *)
(* Julien Narboux (Julien@narboux.fr)                                      *)
(* LIX/INRIA FUTURS 2004-2006                                              *)
(* University of Strasbourg 2008-2009                                      *)
(***************************************************************************)
Require Export euclidean_constructions.
Require Export area_elimination_lemmas.
Require Export ratios_elimination_lemmas.

Lemma perp_not_eq_not_perp : forall A B P D, perp A B P D ->
Col A D B ->
A <> B ->  B <> D -> A <> D ->
Py P A B <> 0.