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(* GNU General Public License for more details.                       *)
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(* 02110-1301 USA                                                     *)
Require Export homographicAcc_Qhomographic_sign.
(** note that ~(`c=0`/\`d=0`)<->`c<>0`\/`c<>d` *)

Lemma Qhomographic_sg_denom_nonzero_nonzero :
forall (c d : Z) (p : Qpositive),
c = 0%Z -> d = 0%Z -> ~ Qhomographic_sg_denom_nonzero c d p.