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

Theorem th6_41_b : forall A B C M N L P K X1 X2:Point,
is_midpoint M A B ->
is_midpoint N A C ->
is_midpoint K B C ->
on_parallel X1 A C M ->
on_parallel X2 K B N ->
inter_ll P X1 A X2 K ->
is_midpoint L A K ->
B<>C ->
parallel L P B C ->
2+2<>0 ->
L<>P ->
L**P / B**C = (1+2)/(2+2).