
theorem Th1234:
Sum digits(2950,10) = 16
proof
  thus Sum digits(2950,10) = Sum <%0,5,9%>+Sum <%2%> by Th1233,AFINSQ_2:55
  .= Sum <%0,5%> + Sum <%9%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 5) + Sum <%9%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 5 + 9) + Sum <%2%> by AFINSQ_2:53
  .= 14 + 2 by AFINSQ_2:53
  .= 16;
end;
