thus Sum (digits (4800,10)) = (Sum <%0,0,8%>) + (Sum <%4%>) by Th1361, AFINSQ_2:55
.= ((Sum <%0,0%>) + (Sum <%8%>)) + (Sum <%4%>) by AFINSQ_2:55
.= ((0 + 0) + (Sum <%8%>)) + (Sum <%4%>) by AFINSQ_2:54
.= ((0 + 0) + 8) + (Sum <%4%>) by AFINSQ_2:53
.= 8 + 4 by AFINSQ_2:53
.= 12 ; :: thesis: verum