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(* as published by the Free Software Foundation; either version 2.1   *)
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(* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the      *)
(* 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` *)

(* Specifications: *)
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.