
theorem Th493:
Sum digits(1640,10) = 11
proof
  thus Sum digits(1640,10) = Sum <%0,4,6%>+Sum <%1%> by Th492,AFINSQ_2:55
  .= Sum <%0,4%> + Sum <%6%> + Sum <%1%> by AFINSQ_2:55
  .= (0 + 4) + Sum <%6%> + Sum <%1%> by AFINSQ_2:54
  .= (0 + 4 + 6) + Sum <%1%> by AFINSQ_2:53
  .= 10 + 1 by AFINSQ_2:53
  .= 11;
end;
