
theorem Th1264:
Sum digits(3450,10) = 12
proof
  thus Sum digits(3450,10) = Sum <%0,5,4%>+Sum <%3%> by Th1263,AFINSQ_2:55
  .= Sum <%0,5%> + Sum <%4%> + Sum <%3%> by AFINSQ_2:55
  .= (0 + 5) + Sum <%4%> + Sum <%3%> by AFINSQ_2:54
  .= (0 + 5 + 4) + Sum <%3%> by AFINSQ_2:53
  .= 9 + 3 by AFINSQ_2:53
  .= 12;
end;
