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

Lemma l7_15 : forall P Q R P' Q' R' A,
Midpoint A P P' -> Midpoint A Q Q' -> Midpoint A R R' -> Bet P Q R -> Bet P' Q' R'.