
theorem Th417:
Sum digits(880,10) = 16
proof
  thus Sum digits(880,10) = Sum <%0,8%>+Sum <%8%> by Th416,AFINSQ_2:55
  .= (0 + 8) + Sum <%8%> by AFINSQ_2:54
  .= 8 + 8 by AFINSQ_2:53
  .= 16;
end;
