Ltac local_uniformize_signed_areas := Runiformize_signed_areas.(*
Ltac local_uniformize_signed_areas := uniformize_signed_areas.
*)

Ltac local_basic_simpl := Rbasic_simpl.Ltac local_uniformize_signed_areas4 := uniformize_signed_areas4.

Lemma test21 : forall A B C D, S4 A B C D = - S4 A D C B.