Section Quadrilateral.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
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Lemma cong3_id : forall A B C D, A <> B -> Col A B C -> Col A B D -> Cong A B C D -> Cong A D B C -> Cong A C B D
-> A = D /\ B = C \/ A = C /\ B = D.