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

Lemma symmetry_preserves_bet :
forall A B M A' B',
Midpoint M A A' ->
Midpoint M B B' ->
(Bet M A' B' <-> Bet M A B).