Section Angles_3.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
Global Instance eqA_equivalence : Equivalence EqA.

Lemma not_null_ang_def_equiv : forall a, Q_CongA_nNull a <-> (Q_CongA a /\ exists A, exists B, exists C, a A B C /\  ~Out B A C).