(***************************************************************************)
(* 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 *)

Lemma test_area_inter_ll_1 : forall I A B C D X Y,
inter_ll I A B C D -> S X Y I = 1 / S4 A C B D * (S A C D * S X Y B + S B D C * S X Y A) .