
theorem Th1063:
Sum digits(696,10) = 21
proof
  thus Sum digits(696,10) = Sum <%6,9%>+Sum <%6%> by Th1062,AFINSQ_2:55
  .= (6 + 9) + Sum <%6%> by AFINSQ_2:54
  .= 15 + 6 by AFINSQ_2:53
  .= 21;
end;
