(** Prop 7   **)

Lemma bet_cop_onc2__ex_onc_os_out : forall O P A B C I,
A <> I -> B <> I -> ~ Col A B C -> ~ Col A B O ->
OnCircle A O P -> OnCircle B O P -> Bet A I B -> Coplanar A B C O ->
exists C1, Out C1 O I /\ OnCircle C1 O P /\ OS A B C C1.