
theorem Th597:
Sum digits(2680,10) = 16
proof
  thus Sum digits(2680,10) = Sum <%0,8,6%>+Sum <%2%> by Th596,AFINSQ_2:55
  .= Sum <%0,8%> + Sum <%6%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 8) + Sum <%6%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 8 + 6) + Sum <%2%> by AFINSQ_2:53
  .= 14 + 2 by AFINSQ_2:53
  .= 16;
end;
