(** This is SSA congruence with a right angle *)

Lemma cop3_orth_at__orth_at : forall A B C D E F U V X, ~ Col D E F ->
Coplanar A B C D -> Coplanar A B C E -> Coplanar A B C F -> Orth_at X A B C U V ->
Orth_at X D E F U V.