(** This version uses an extra point *)

(* Specifications: *)
Theorem Pappus_2 : forall A B C A' B' C' P Q R T:Point,
on_line C A B ->
on_line C' A' B' ->
inter_ll P A' B A B' ->
inter_ll Q A C' A' C ->
inter_ll R B' C B C' ->
inter_ll T B' C P Q ->
C<>R -> C<>T ->
parallel B' R C R ->
parallel B' T C T ->
B'**R / C**R = B'**T / C**T.