
theorem Th577:
Sum digits(2480,10) = 14
proof
  thus Sum digits(2480,10) = Sum <%0,8,4%>+Sum <%2%> by Th576,AFINSQ_2:55
  .= Sum <%0,8%> + Sum <%4%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 8) + Sum <%4%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 8 + 4) + Sum <%2%> by AFINSQ_2:53
  .= 12 + 2 by AFINSQ_2:53
  .= 14;
end;
