thus Sum (digits (2380,10)) = (Sum <%0,8,3%>) + (Sum <%2%>) by Th566, AFINSQ_2:55
.= ((Sum <%0,8%>) + (Sum <%3%>)) + (Sum <%2%>) by AFINSQ_2:55
.= ((0 + 8) + (Sum <%3%>)) + (Sum <%2%>) by AFINSQ_2:54
.= ((0 + 8) + 3) + (Sum <%2%>) by AFINSQ_2:53
.= 11 + 2 by AFINSQ_2:53
.= 13 ; :: thesis: verum