Require Export GeoCoq.Elements.OriginalProofs.lemma_parallelNC.
Require Export GeoCoq.Elements.OriginalProofs.lemma_crossimpliesopposite.
Require Export GeoCoq.Elements.OriginalProofs.proposition_34.
Require Export GeoCoq.Elements.OriginalProofs.lemma_NCdistinct.
Section Euclid.
Context `{Ax:euclidean_euclidean}.

(* Specifications: *)
Lemma lemma_diagonalsbisect :
forall A B C D,
PG A B C D ->
exists X, Midpoint A X C /\ Midpoint B X D.