Section playfair_par_trans.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
(** This is Legendre theorem XXV http://gallica.bnf.fr/ark:/12148/bpt6k202689z/f29.image *)

(* Specifications: *)
Lemma playfair_implies_par_trans :
playfair_s_postulate -> postulate_of_transitivity_of_parallelism.