
theorem Th258:
Sum digits(408,10) = 12
proof
  thus Sum digits(408,10) = Sum <%8,0%>+Sum <%4%> by Th257,AFINSQ_2:55
  .= (8 + 0) + Sum <%4%> by AFINSQ_2:54
  .= 8 + 4 by AFINSQ_2:53
  .= 12;
end;
