thus Sum (digits (2940,10)) = (Sum <%0,4,9%>) + (Sum <%2%>) by Th622, AFINSQ_2:55
.= ((Sum <%0,4%>) + (Sum <%9%>)) + (Sum <%2%>) by AFINSQ_2:55
.= ((0 + 4) + (Sum <%9%>)) + (Sum <%2%>) by AFINSQ_2:54
.= ((0 + 4) + 9) + (Sum <%2%>) by AFINSQ_2:53
.= 13 + 2 by AFINSQ_2:53
.= 15 ; :: thesis: verum