
theorem Th399:
Sum digits(680,10) = 14
proof
  thus Sum digits(680,10) = Sum <%0,8%>+Sum <%6%> by Th398,AFINSQ_2:55
  .= (0 + 8) + Sum <%6%> by AFINSQ_2:54
  .= 8 + 6 by AFINSQ_2:53
  .= 14;
end;
