Hint Resolve not_cong_2134 not_cong_1243 not_cong_2143
not_cong_3412 not_cong_4312 not_cong_3421 not_cong_4321 : cong.
Section T1_3.
Context `{Tn:Tarski_neutral_dimensionless}.

Lemma cong_diff_4 : forall A B C D ,
D <> C -> Cong A B C D -> A <> B.