thus Sum (digits (3300,10)) = (Sum <%0,0,3%>) + (Sum <%3%>) by Th658, AFINSQ_2:55
.= ((Sum <%0,0%>) + (Sum <%3%>)) + (Sum <%3%>) by AFINSQ_2:55
.= ((0 + 0) + (Sum <%3%>)) + (Sum <%3%>) by AFINSQ_2:54
.= ((0 + 0) + 3) + (Sum <%3%>) by AFINSQ_2:53
.= 3 + 3 by AFINSQ_2:53
.= 6 ; :: thesis: verum