
theorem Th264:
Sum digits(459,10) = 18
proof
  thus Sum digits(459,10) = Sum <%9,5%>+Sum <%4%> by Th263,AFINSQ_2:55
  .= (9 + 5) + Sum <%4%> by AFINSQ_2:54
  .= 14 + 4 by AFINSQ_2:53
  .= 18;
end;
