(** * Proposition 19 In any triangle the greater angle is subtended by the greater side. *)
(** # <div style="width:748px;height:397px;display:block" id="applet_container19"></div> # **)

Lemma prop_19 : forall A B C, ~ Col A B C -> LtA B C A A B C -> LtA C A B A B C ->
Lt A B A C /\ Lt B C A C.