
theorem Th176:
Sum digits(135,10) = 9
proof
  thus Sum digits(135,10) = Sum <%5,3%>+Sum <%1%> by Th175,AFINSQ_2:55
  .= (5 + 3) + Sum <%1%> by AFINSQ_2:54
  .= 8 + 1 by AFINSQ_2:53
  .= 9;
end;
