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 image_in_col : forall A B P P' Y : Tpoint,
ReflectL_at Y P P' A B -> Col P P' Y.