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I am having some difficulty when dealing with complex number using mathematica function Abs. I am trying to use Abs[1+ I w] to get Abs[1+ I w]=Sqrt[1+ w^2]. But, it seems that I can't do it in a straight forward way. That is ...
thanks for the suggested solution. It has now been fixed.
Thanks for your reply.  Really appreciate it. I use ver  windows 7.  Obviously, there might be a little unexpected behaviour here with Ver. 8. I don't know what to do. I am currently thinking about upgrading to the latest version.