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

Lemma null_anga : forall A B C D a1 a2, Ang_Acute A B A a1 -> Ang_Acute C D C a2 -> EqA a1 a2.