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Re: ComplexExpand confusion

• To: mathgroup at smc.vnet.net
• Subject: [mg60141] Re: [mg60109] ComplexExpand confusion
• From: "David Park" <djmp at earthlink.net>
• Date: Sun, 4 Sep 2005 03:02:04 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

Mike,

The answer is very simple! Just look at...

ComplexExpand[(-1)^(1/4)] // Trace

Could anything be clearer?

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/ 


From: mike_in_england2000 at yahoo.co.uk
To: mathgroup at smc.vnet.net
[mailto:mike_in_england2000 at yahoo.co.uk]


Hi

The Mathematica help system says that

"ComplexExpand[expr] expands expr assuming that all variables are
real."

which is fine and explains why expressions such as
ComplexExpand[Conjugate[x +I y]] work.All seems obvious so far.

What is confusing me though is why does

ComplexExpand[(-1)^(1/4)]

give the result

(1 + I)/Sqrt[2]

I know this the correct result but in the expression (-1)^(1/4) there
are no variables.  The numbers involved are real so what on earth is
ComplexExpand doing? Is this a stupid question? Should I have drank
more coffee before posting this.

Thanks
Mike

• Follow-Ups:
  • Re: Re: ComplexExpand confusion
    • From: Chris Chiasson <chris.chiasson@gmail.com>