Section T10_1.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.

Lemma cop_not_par_same_side :
forall A B C D I P, C <> D -> Col A B I -> Col C D I -> ~ Col A B C -> ~ Col A B P ->
Coplanar A B C P ->
exists Q, Col C D Q /\ OS A B P Q.