thus Sum (digits (2620,10)) = (Sum <%0,2,6%>) + (Sum <%2%>) by Th590, AFINSQ_2:55
.= ((Sum <%0,2%>) + (Sum <%6%>)) + (Sum <%2%>) by AFINSQ_2:55
.= ((0 + 2) + (Sum <%6%>)) + (Sum <%2%>) by AFINSQ_2:54
.= ((0 + 2) + 6) + (Sum <%2%>) by AFINSQ_2:53
.= 8 + 2 by AFINSQ_2:53
.= 10 ; :: thesis: verum