Section Quadrilateral.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.

Lemma col_cong_mid :
forall A B A' B',
Par A B A' B' ->
~ Par_strict A B A' B' ->
Cong A B A' B' ->
exists M,  Midpoint M A A' /\ Midpoint M B B' \/
Midpoint M A B' /\ Midpoint M B A'.