(** Euclid Book III Prop 22: The opposite angles of quadrilaterals in circles are equal to two right angles. *)

Lemma cop_onc4_ts__suppa : forall O P A B C C',
OnCircle A O P -> OnCircle B O P -> OnCircle C O P -> OnCircle C' O P ->
TS A B C C' -> Coplanar A B C O ->
SuppA A C B A C' B.