(** 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 cop_tsp__ex_cop2 : forall A B C D E P,
Coplanar A B C P -> TSP A B C D E ->
exists Q, Coplanar A B C Q /\ Coplanar D E P Q /\ P <> Q.