(** on_line_d *)

(* Specifications: *)
Lemma test_area_on_line_d_1 : forall I B C, forall x:F,
on_line_d I B C x -> S B I C = 0.
Lemma test_area_on_line_d_2 : forall I B C, forall x:F,
on_line_d I B C x -> S I B C = 0.
Lemma test_area_on_line_d_3 : forall I B C, forall x:F,
on_line_d I B C x -> S B C I = 0.