
theorem Th599:
Sum digits(2700,10) = 9
proof
  thus Sum digits(2700,10) = Sum <%0,0,7%>+Sum <%2%> by Th598,AFINSQ_2:55
  .= Sum <%0,0%> + Sum <%7%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 0) + Sum <%7%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 0 + 7) + Sum <%2%> by AFINSQ_2:53
  .= 7 + 2 by AFINSQ_2:53
  .= 9;
end;
