(***************************************************************************)
(* Formalization of the Chou, Gao and Zhang's decision procedure.          *)
(* Julien Narboux (Julien@narboux.fr)                                      *)
(* LIX/INRIA FUTURS 2004-2006                                              *)
(* University of Strasbourg 2008                                           *)
(***************************************************************************)
(** Area elimination *)
(** on_line *)
(** on_line_d *)
(* inter_ll *)
(* on_foot *)
(* on_perp_d *)
(* on_perp *)

Lemma test_area_on_perp_1  : forall I X Y A B,
on_perp I X Y -> S I A B = S I A B.