(** The sum of the angles of a degenerate triangle is a straight angle *)

(* Specifications: *)
Lemma col_trisuma__bet : forall A B C P Q R, Col A B C -> TriSumA A B C P Q R -> Bet P Q R.
(** Decidability properties *)
Lemma suma_dec : forall A B C D E F G H I, SumA A B C D E F G H I \/ ~ SumA A B C D E F G H I.
Lemma sams_dec : forall A B C D E F, SAMS A B C D E F \/ ~ SAMS A B C D E F.
Lemma trisuma_dec : forall A B C P Q R, TriSumA A B C P Q R \/ ~ TriSumA A B C P Q R.
End Suma_2.