Section Angles_2.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.

Lemma flat_ang : forall A B C A' B' C' a1 a2, Bet A B C -> Bet A' B' C' -> Ang A B C a1 -> Ang A' B' C' a2  -> EqA a1 a2.