
theorem Th60:
Sum digits(33,10) = 6
proof
  thus Sum digits(33,10) = Sum <%3%>+Sum <%3%> by Th59,AFINSQ_2:55
  .= 3 + Sum <%3%> by AFINSQ_2:53
  .= 3+3 by AFINSQ_2:53
  .= 6;
end;
