thus Sum (digits (2325,10)) = (Sum <%5,2,3%>) + (Sum <%2%>) by Th1195, AFINSQ_2:55
.= ((Sum <%5,2%>) + (Sum <%3%>)) + (Sum <%2%>) by AFINSQ_2:55
.= ((5 + 2) + (Sum <%3%>)) + (Sum <%2%>) by AFINSQ_2:54
.= ((5 + 2) + 3) + (Sum <%2%>) by AFINSQ_2:53
.= 10 + 2 by AFINSQ_2:53
.= 12 ; :: thesis: verum