thus Sum (digits (4650,10)) = (Sum <%0,5,6%>) + (Sum <%4%>) by Th1349, AFINSQ_2:55
.= ((Sum <%0,5%>) + (Sum <%6%>)) + (Sum <%4%>) by AFINSQ_2:55
.= ((0 + 5) + (Sum <%6%>)) + (Sum <%4%>) by AFINSQ_2:54
.= ((0 + 5) + 6) + (Sum <%4%>) by AFINSQ_2:53
.= 11 + 4 by AFINSQ_2:53
.= 15 ; :: thesis: verum