reserve A for QC-alphabet;
reserve i,j,k,l,m,n for Nat;
reserve a,b,e for set;
reserve t,u,v,w,z for QC-symbol of A;
reserve p,q,r,s for Element of CQC-WFF(A);
reserve x for Element of bound_QC-variables(A);
reserve ll for CQC-variable_list of k,A;
reserve P for QC-pred_symbol of k,A;
reserve f,h for Element of Funcs(bound_QC-variables(A),bound_QC-variables(A)),
  K,L for Element of Fin bound_QC-variables(A);

theorem Th28:
  SepVar 'not' p = 'not' SepVar p
proof
  reconsider FP = (SepFunc(A)).p as Function of
   [:QC-symbols(A),Funcs(bound_QC-variables(A), bound_QC-variables(A)):],
    CQC-WFF(A);
  thus SepVar 'not' p =(NEGATIVE FP).[index ('not' p),id bound_QC-variables(A)]
  by Def7
    .= (NEGATIVE FP).[index p,(id bound_QC-variables(A))] by Th23
    .= 'not' SepVar p by Def2;
end;
