(* Gabriel Braun November 2012 *)
Require Export GeoCoq.Tarski_dev.Ch12_parallel.
Section Quadrilateral.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.

Lemma mid_plgf_aux :
forall A B C D M,
A <> C ->
Col A B C ->
Midpoint M A C -> Midpoint M B D ->
Parallelogram_flat A B C D.