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

Lemma l3_51: forall A B C D J M N,
on_foot D A B C ->
on_line J A D ->
inter_ll M A B C J ->
inter_ll N A C B J ->
eq_angle M D A A D N.