(** * Proposition 18 In any triangle the greater side subtends the greater angle. *)
(** # <div style="width:748px;height:397px;display:block" id="applet_container18"></div> # **)

Lemma prop_18 : forall A B C, ~ Col A B C -> Lt A B A C -> Lt B C A C ->
LtA B C A A B C /\ LtA C A B A B C.