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 bet_cong3 : forall A B C A' B',  Bet A B C -> Cong A B A' B' -> exists C', Cong_3 A B C A' B' C'.