(* Gabriel Braun April 2013 *)
Require Export GeoCoq.Tarski_dev.Ch12_parallel.
Section L13_1.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
(** Pappus Desargues *)

Lemma perp_bet_obtuse : forall A B C C', B <> C' -> Perp A B C C' -> Bet A B C' -> Obtuse A B C.
End L13_1.