
theorem Th1256:
Sum digits(3325,10) = 13
proof
  thus Sum digits(3325,10) = Sum <%5,2,3%>+Sum <%3%> by Th1255,AFINSQ_2:55
  .= Sum <%5,2%> + Sum <%3%> + Sum <%3%> by AFINSQ_2:55
  .= (5 + 2) + Sum <%3%> + Sum <%3%> by AFINSQ_2:54
  .= (5 + 2 + 3) + Sum <%3%> by AFINSQ_2:53
  .= 10 + 3 by AFINSQ_2:53
  .= 13;
end;
