Require Export GeoCoq.Tarski_dev.Ch11_angles.
Section T12_1.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.

Lemma Par_strict_cases :
forall A B C D,
Par_strict A B C D \/ Par_strict B A C D \/ Par_strict A B D C \/ Par_strict B A D C \/
Par_strict C D A B \/ Par_strict C D B A \/ Par_strict D C A B \/ Par_strict D C B A ->
Par_strict A B C D.