Require Export GeoCoq.Elements.OriginalProofs.lemma_crisscross.
Section Euclid.
Context `{Ax1:euclidean_neutral_ruler_compass}.

(* Specifications: *)
Lemma lemma_30helper :
forall A B E F G H,
Par A B E F -> BetS A G B -> BetS E H F -> ~ CR A F G H ->
CR A E G H.