
theorem Th425:
Sum digits(960,10) = 15
proof
  thus Sum digits(960,10) = Sum <%0,6%>+Sum <%9%> by Th424,AFINSQ_2:55
  .= (0 + 6) + Sum <%9%> by AFINSQ_2:54
  .= 6 + 9 by AFINSQ_2:53
  .= 15;
end;
