Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2005
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2005

[Date Index] [Thread Index] [Author Index]

Search the Archive

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





  • Prev by Date: Re: ComplexExpand confusion
  • Next by Date: Re: Timing loop For !!
  • Previous by thread: Re: ComplexExpand confusion
  • Next by thread: Re: Re: ComplexExpand confusion