End Beeson_1.
Section Beeson_2.
Context `{Tn:Tarski_neutral_dimensionless}.
Variable Bet_stability : forall A B C, ~ ~ Bet A B C -> Bet A B C.

Lemma BetSEq : forall A B C, BetS A B C <-> Bet A B C /\ A <> B /\ A <> C /\ B <> C.
End Beeson_2.