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
  p is negative & q = the_argument_of p implies SepVar p = 'not' SepVar q
proof
  assume that
A1: p is negative and
A2: q = the_argument_of p;
  p = 'not' q by A1,A2,QC_LANG1:def 24;
  hence thesis by Th28;
end;
