
theorem Th397:
Sum digits(660,10) = 12
proof
  thus Sum digits(660,10) = Sum <%0,6%>+Sum <%6%> by Th396,AFINSQ_2:55
  .= (0 + 6) + Sum <%6%> by AFINSQ_2:54
  .= 6 + 6 by AFINSQ_2:53
  .= 12;
end;
