thus Sum (digits (3740,10)) = (Sum <%0,4,7%>) + (Sum <%3%>) by Th702, AFINSQ_2:55
.= ((Sum <%0,4%>) + (Sum <%7%>)) + (Sum <%3%>) by AFINSQ_2:55
.= ((0 + 4) + (Sum <%7%>)) + (Sum <%3%>) by AFINSQ_2:54
.= ((0 + 4) + 7) + (Sum <%3%>) by AFINSQ_2:53
.= 11 + 3 by AFINSQ_2:53
.= 14 ; :: thesis: verum