Section T7_1.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
(** This corresponds to l7_8 in Tarski's book. *)

Lemma symmetry_preserves_midpoint :
forall A B C D E F Z,
Midpoint Z A D -> Midpoint Z B E ->
Midpoint Z C F -> Midpoint B A C -> Midpoint E D F.