
theorem Th1069:
Sum digits(816,10) = 15
proof
  thus Sum digits(816,10) = Sum <%6,1%>+Sum <%8%> by Th1068,AFINSQ_2:55
  .= (6 + 1) + Sum <%8%> by AFINSQ_2:54
  .= 7 + 8 by AFINSQ_2:53
  .= 15;
end;
