Require Export GeoCoq.Elements.OriginalProofs.lemma_Euclid4.
Require Export GeoCoq.Elements.OriginalProofs.proposition_28C.
Require Export GeoCoq.Elements.OriginalProofs.lemma_parallelflip.
Section Euclid.
Context `{Ax1:euclidean_neutral_ruler_compass}.

Lemma lemma_twoperpsparallel :
forall A B C D,
Per A B C -> Per B C D -> OS A D B C ->
Par A B C D.