(** This lemma used to be an axiom in previous versions of Tarski's axiom system. It is a been shown to a theorem by Gupta in his Phd 1965. *)
(** This corresponds to l9_6 in Tarski's book. *)

Lemma coplanar_pseudo_trans : forall A B C D P Q R,
~ Col P Q R ->
Coplanar P Q R A ->
Coplanar P Q R B ->
Coplanar P Q R C ->
Coplanar P Q R D ->
Coplanar A B C D.