(***************************************************************************)
(* Formalization of the Chou, Gao and Zhang's decision procedure.          *)
(* Julien Narboux (Julien@narboux.fr)                                      *)
(* LIX/INRIA FUTURS 2004-2006                                              *)
(* University of Strasbourg 2008                                           *)
(***************************************************************************)
Require Export field_general_properties.
Require Export chou_gao_zhang_axioms.
(* This file contains the lemmas needed by the tactics used as tools for both the development and the decision procedure. *)
(********************************************************)
(* Signed areas                                         *)
(********************************************************)

Lemma S_0 : forall A B C : Point, S A B C = S C A B.
auto with Geom.