Section Inscribed_angle.
Context `{TE:Tarski_euclidean}.
(** The sum of the angles of a triangle is the flat angle. *)

Lemma bet__trisuma : forall A B C D E F, Bet D E F -> A <> B -> B <> C -> A <> C -> D <> E -> E <> F ->
TriSumA A B C D E F.