(** * Proposition 14 If with any straight line, and at a point on it, two straight lines not lying on the same side make the adjacent angles equal to two right angles, the two straight lines will be in a straight line with one another. *)
(** # <div style="width:748px;height:397px;display:block" id="applet_container14"></div> # **)

(* Specifications: *)
Lemma prop_14 : forall A B C D P Q R S T U, TS A B C D -> Per P Q R ->
SumA A B C A B D S T U -> SumA P Q R P Q R S T U -> Bet C B D.