Lemma conga_cop_onc6_os__eq : forall A B C D O P O' P', OnCircle A O P -> OnCircle B O P -> OnCircle C O P -> Coplanar A B C O -> OnCircle A O' P' -> OnCircle B O' P' -> OnCircle D O' P' -> Coplanar A B D O' -> OS A B C D -> CongA A C B A D B -> (O = O' /\ Cong O P O' P').