Hint Immediate col_trivial_1 col_trivial_2 col_trivial_3: col.
Section T4_4.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.

Lemma l4_19 : forall A B C C',
Bet A C B -> Cong A C A C' -> Cong B C B C' -> C=C'.