Require Export GeoCoq.Elements.OriginalProofs.lemma_samesidesymmetric.
Require Export GeoCoq.Elements.OriginalProofs.lemma_planeseparation.
Section Euclid.
Context `{Ax:euclidean_neutral_ruler_compass}.

(* Specifications: *)
Lemma lemma_samenotopposite :
forall A B C D,
OS A B C D ->
~ TS A C D B.