thus Sum (digits (3125,10)) = (Sum <%5,2,1%>) + (Sum <%3%>) by Th1243, AFINSQ_2:55
.= ((Sum <%5,2%>) + (Sum <%1%>)) + (Sum <%3%>) by AFINSQ_2:55
.= ((5 + 2) + (Sum <%1%>)) + (Sum <%3%>) by AFINSQ_2:54
.= ((5 + 2) + 1) + (Sum <%3%>) by AFINSQ_2:53
.= 8 + 3 by AFINSQ_2:53
.= 11 ; :: thesis: verum