
theorem Th1049:
Sum digits(216,10) = 9
proof
  thus Sum digits(216,10) = Sum <%6,1%>+Sum <%2%> by Th1048,AFINSQ_2:55
  .= (6 + 1) + Sum <%2%> by AFINSQ_2:54
  .= 7 + 2 by AFINSQ_2:53
  .= 9;
end;
