theorem Th62:
  for a being non positive expression of C, an_Adj C
  holds (non_op C)term (Non a) = a
proof
  let a be non positive expression of C, an_Adj C;
  ex a9 being expression of C, an_Adj C st ( a = (non_op C)
  term a9)&( Non a = a9) by Th60;
  hence thesis;
end;
