thus Sum (digits (1196,10)) = (Sum <%6,9,1%>) + (Sum <%1%>) by Th1007, AFINSQ_2:55
.= ((Sum <%6,9%>) + (Sum <%1%>)) + (Sum <%1%>) by AFINSQ_2:55
.= ((6 + 9) + (Sum <%1%>)) + (Sum <%1%>) by AFINSQ_2:54
.= ((6 + 9) + 1) + (Sum <%1%>) by AFINSQ_2:53
.= 16 + 1 by AFINSQ_2:53
.= 17 ; :: thesis: verum