(** 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 l9_30 : forall A B C D E F P X Y Z,
~ Coplanar A B C P -> ~ Col D E F -> Coplanar D E F P ->
Coplanar A B C X -> Coplanar A B C Y -> Coplanar A B C Z ->
Coplanar D E F X -> Coplanar D E F Y -> Coplanar D E F Z ->
Col X Y Z.