
theorem Th170:
Sum digits(45,10) = 9
proof
  thus Sum digits(45,10) = Sum <%5%>+Sum <%4%> by Th169,AFINSQ_2:55
  .= 5 + Sum <%4%> by AFINSQ_2:53
  .= 5+4 by AFINSQ_2:53
  .= 9;
end;
