(* Lemma test_on_line_d_13 : forall Y P Q A C D lambda, on_line_d Y P Q lambda ->  Y<>A -> parallel C D Y A -> False -> C**D/Y**A = C**D. *)
(** Test inter_ll in a ratio *)
(** Test cases where Y occurs both in denominator and numerator *)

Lemma test_inter_ll : forall T P Q A B C D,
inter_ll T A B C D->
parallel T P T Q ->
T<>Q ->
P<>T ->
T ** P / T ** Q = T ** P / T ** Q + 1 - 1.