
theorem Th569:
Sum digits(2400,10) = 6
proof
  thus Sum digits(2400,10) = Sum <%0,0,4%>+Sum <%2%> by Th568,AFINSQ_2:55
  .= Sum <%0,0%> + Sum <%4%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 0) + Sum <%4%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 0 + 4) + Sum <%2%> by AFINSQ_2:53
  .= 4 + 2 by AFINSQ_2:53
  .= 6;
end;
