End T1_3.
Hint Resolve cong_3_sym : cong.
Hint Resolve cong_3_swap cong_3_swap_2 cong3_transitivity : cong3.
Hint Unfold Cong_3 : cong3.
Section T1_4.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.

Lemma Cong_cases :
forall A B C D,
Cong A B C D \/ Cong A B D C \/ Cong B A C D \/ Cong B A D C \/
Cong C D A B \/ Cong C D B A \/ Cong D C A B \/ Cong D C B A ->
Cong A B C D.