
theorem Th1330:
Sum digits(4400,10) = 8
proof
  thus Sum digits(4400,10) = Sum <%0,0,4%>+Sum <%4%> by Th1329,AFINSQ_2:55
  .= Sum <%0,0%> + Sum <%4%> + Sum <%4%> by AFINSQ_2:55
  .= (0 + 0) + Sum <%4%> + Sum <%4%> by AFINSQ_2:54
  .= (0 + 0 + 4) + Sum <%4%> by AFINSQ_2:53
  .= 4 + 4 by AFINSQ_2:53
  .= 8;
end;
