theorem Th6:
  P is QC-pred_symbol of k,Al2
proof
  the_arity_of P = k by QC_LANG1:11;
  then
A1: P`1 = 7+k by QC_LANG1:def 8;
  reconsider P as QC-pred_symbol of Al2 by Th3,TARSKI:def 3;
  the_arity_of P = k by QC_LANG1:def 8, A1;
  hence thesis by QC_LANG3:1;
end;
