
theorem Th771:
Sum digits(572,10) = 14
proof
  thus Sum digits(572,10) = Sum <%2,7%>+Sum <%5%> by Th770,AFINSQ_2:55
  .= (2 + 7) + Sum <%5%> by AFINSQ_2:54
  .= 9 + 5 by AFINSQ_2:53
  .= 14;
end;
