
theorem Th697:
Sum digits(3680,10) = 17
proof
  thus Sum digits(3680,10) = Sum <%0,8,6%>+Sum <%3%> by Th696,AFINSQ_2:55
  .= Sum <%0,8%> + Sum <%6%> + Sum <%3%> by AFINSQ_2:55
  .= (0 + 8) + Sum <%6%> + Sum <%3%> by AFINSQ_2:54
  .= (0 + 8 + 6) + Sum <%3%> by AFINSQ_2:53
  .= 14 + 3 by AFINSQ_2:53
  .= 17;
end;
