Re: ComplexExpand confusion

• To: mathgroup at smc.vnet.net
• Subject: [mg60135] Re: [mg60109] ComplexExpand confusion
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Sun, 4 Sep 2005 03:01:58 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

```The Further Examples for ComplexExpand states that it will expand complex
powers, i.e., it is converting from the polar form of the complex number to its
Cartesian form.

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

(1 + I)/Sqrt[2]

%//FullSimplify

(-1)^(1/4)

You get the same result with ExpToTrig

(-1)^(1/4)//ExpToTrig

(1 + I)/Sqrt[2]

Bob Hanlon

>
> From: mike_in_england2000 at yahoo.co.uk
To: mathgroup at smc.vnet.net
> Date: 2005/09/03 Sat AM 02:05:58 EDT
> Subject: [mg60135] [mg60109] ComplexExpand confusion
>
> 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: Timing loop For !!
• Next by Date: Re: Please explain this weird Integrate result
• Previous by thread: Re: Re: ComplexExpand confusion
• Next by thread: Re: Re: ComplexExpand confusion