thus Sum (digits (1058,10)) = (Sum <%8,5,0%>) + (Sum <%1%>) by Th995, AFINSQ_2:55
.= ((Sum <%8,5%>) + (Sum <%0%>)) + (Sum <%1%>) by AFINSQ_2:55
.= ((8 + 5) + (Sum <%0%>)) + (Sum <%1%>) by AFINSQ_2:54
.= ((8 + 5) + 0) + (Sum <%1%>) by AFINSQ_2:53
.= 13 + 1 by AFINSQ_2:53
.= 14 ; :: thesis: verum