Section T10.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
Goal forall A B C D, ~ Coplanar D C B A -> ~ Coplanar A B C D.

Lemma ex_per_cong : forall A B C D X Y,
A <> B -> X <> Y -> Col A B C -> ~Col A B D ->
exists P, Per P C A /\ Cong P C X Y /\ OS A B P D.