
theorem Th1080:
Sum digits(175,10) = 13
proof
  thus Sum digits(175,10) = Sum <%5,7%>+Sum <%1%> by Th1079,AFINSQ_2:55
  .= (5 + 7) + Sum <%1%> by AFINSQ_2:54
  .= 12 + 1 by AFINSQ_2:53
  .= 13;
end;
