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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 th6_258 : forall A B C D E F M N P Q:Point,
on_parallel_d D B E A 1 ->
on_line C A E ->
on_line F B D ->
inter_ll M D C A F ->
inter_ll N E F B C ->
inter_ll P M N A D ->
inter_ll Q M N E B ->
D<>P -> E<>Q ->
parallel A P D P ->
parallel B Q E Q ->
A**P/D**P=B**Q/E**Q.