
theorem Th391:
Sum digits(600,10) = 6
proof
  thus Sum digits(600,10) = Sum <%0,0%>+Sum <%6%> by Th390,AFINSQ_2:55
  .= (0 + 0) + Sum <%6%> by AFINSQ_2:54
  .= 6 by AFINSQ_2:53;
end;
