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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 ex1_6auto :
forall A B C D E F G P : Point,
inter_ll D B C A P ->
inter_ll E A C B P ->
inter_ll F A B C P ->
A <> D ->
B <> E ->
C <> F ->
parallel P D A D ->
parallel P E B E ->
parallel P F C F ->
P ** D / A ** D + P ** E / B ** E + P ** F / C ** F = 1.