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 l10_5 : forall A B P P' P'',
Reflect P' P A B ->
Reflect P'' P' A B -> P=P''.