(***************************************************************************)
(* Formalization of the Chou, Gao and Zhang's decision procedure.          *)
(* Julien Narboux (Julien@narboux.fr)                                      *)
(* LIX/INRIA FUTURS 2004-2006                                              *)
(* University of Strasbourg 2008                                           *)
(***************************************************************************)

Lemma l_6_273 : forall B C X A A1 C1,
on_perp_d A B C 1 ->
on_foot A1 A B X ->
on_foot C1 C B X ->
eq_distance A A1 B C1.