thus Sum (digits (4550,10)) = (Sum <%0,5,5%>) + (Sum <%4%>) by Th1341, AFINSQ_2:55
.= ((Sum <%0,5%>) + (Sum <%5%>)) + (Sum <%4%>) by AFINSQ_2:55
.= ((0 + 5) + (Sum <%5%>)) + (Sum <%4%>) by AFINSQ_2:54
.= ((0 + 5) + 5) + (Sum <%4%>) by AFINSQ_2:53
.= 10 + 4 by AFINSQ_2:53
.= 14 ; :: thesis: verum