
theorem Th966:
Sum digits(644,10) = 14
proof
  thus Sum digits(644,10) = Sum <%4,4%>+Sum <%6%> by Th965,AFINSQ_2:55
  .= (4 + 4) + Sum <%6%> by AFINSQ_2:54
  .= 8 + 6 by AFINSQ_2:53
  .= 14;
end;
