thus Sum (digits (650,10)) = (Sum <%0,5%>) + (Sum <%6%>) by Th1099, AFINSQ_2:55
.= (0 + 5) + (Sum <%6%>) by AFINSQ_2:54
.= 5 + 6 by AFINSQ_2:53
.= 11 ; :: thesis: verum