Section par_perp_2_par_par_perp_perp.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.

Lemma par_perp_2_par_implies_par_perp_perp :
postulate_of_parallelism_of_perpendicular_transversals ->
perpendicular_transversal_postulate.