
theorem Th970:
Sum digits(690,10) = 15
proof
  thus Sum digits(690,10) = Sum <%0,9%>+Sum <%6%> by Th969,AFINSQ_2:55
  .= (0 + 9) + Sum <%6%> by AFINSQ_2:54
  .= 9 + 6 by AFINSQ_2:53
  .= 15;
end;
