Section Angles_3.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.

Lemma not_cong_is_anga1 : forall A B C A' B' C' a , ~ CongA A B C A' B' C' -> Ang_Acute A B C a -> ~ Ang_Acute A' B' C' a.