
theorem Th409:
Sum digits(800,10) = 8
proof
  thus Sum digits(800,10) = Sum <%0,0%>+Sum <%8%> by Th408,AFINSQ_2:55
  .= (0 + 0) + Sum <%8%> by AFINSQ_2:54
  .= 8 by AFINSQ_2:53;
end;
