Require Export GeoCoq.Elements.OriginalProofs.lemma_midpointunique.
Require Export GeoCoq.Elements.OriginalProofs.lemma_collinear4.
Section Euclid.
Context `{Ax:euclidean_neutral_ruler_compass}.

(* Specifications: *)
Lemma lemma_rightangleNC :
forall A B C,
Per A B C ->
nCol A B C.