thus Sum (digits (1188,10)) = (Sum <%8,8,1%>) + (Sum <%1%>) by Th818, AFINSQ_2:55
.= ((Sum <%8,8%>) + (Sum <%1%>)) + (Sum <%1%>) by AFINSQ_2:55
.= ((8 + 8) + (Sum <%1%>)) + (Sum <%1%>) by AFINSQ_2:54
.= ((8 + 8) + 1) + (Sum <%1%>) by AFINSQ_2:53
.= 17 + 1 by AFINSQ_2:53
.= 18 ; :: thesis: verum