Require Export GeoCoq.Tarski_dev.Ch10_line_reflexivity.
Section T10_1.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.

Lemma not_par_two_sides :
forall A B C D I, C <> D -> Col A B I -> Col C D I -> ~ Col A B C ->
exists X, exists Y, Col C D X /\ Col C D Y /\ TS A B X Y.