
theorem Th1250:
Sum digits(3225,10) = 12
proof
  thus Sum digits(3225,10) = Sum <%5,2,2%>+Sum <%3%> by Th1249,AFINSQ_2:55
  .= Sum <%5,2%> + Sum <%2%> + Sum <%3%> by AFINSQ_2:55
  .= (5 + 2) + Sum <%2%> + Sum <%3%> by AFINSQ_2:54
  .= (5 + 2 + 2) + Sum <%3%> by AFINSQ_2:53
  .= 9 + 3 by AFINSQ_2:53
  .= 12;
end;
