Section T3.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.

Lemma l4_3_1 : forall A B C A' B' C',
Bet A B C -> Bet A' B' C' -> Cong A B A' B' -> Cong A C A' C' -> Cong B C B' C'.