Re: ComplexExpand & ExpIntegralEi
- To: mathgroup at smc.vnet.net
- Subject: [mg31845] Re: [mg31821] ComplexExpand & ExpIntegralEi
- From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
- Date: Fri, 7 Dec 2001 05:56:27 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
You can avoid this problem by setting the option TargetFunctions to
{Re,Im}:
In[2]:=
ComplexExpand[Conjugate[ExpIntegralEi[I x/a]],TargetFunctions->{Re,Im}]
Out[2]=
I x I x
I Im[ExpIntegralEi[-(---)]] + Re[ExpIntegralEi[-(---)]]
a a
It seems if ComplexExpand is allowed to use Conjugate as a
TargetFunction it will not remove it in cases like:
In[9]:=
ComplexExpand[F[Conjugate[x]]]
Out[9]=
F[Conjugate[x]]
although it will do so if F is replaced by many standard functions, e.g.:
In[11]:=
ComplexExpand[Sin[Conjugate[x]]]
Out[11]=
Sin[x]
but not
In[12]:=
ComplexExpand[ExpIntegralEi[Conjugate[x]]]
In[12]:=
ComplexExpand[ExpIntegralEi[Conjugate[x]]]
Out[12]=
I Im[ExpIntegralEi[Conjugate[x]]] +
Re[ExpIntegralEi[Conjugate[x]]]
If you use TargetFunctions to "ban" Conjugate you will ge the expression
you expected. It indeed looks like a bug to me.
Andrzej Kozlowski
Toyama International University
JAPAN
http://platon.c.u-tokyo.ac.jp/andrzej/
On Wednesday, December 5, 2001, at 08:51 PM, Blimbaum Jerry DLPC wrote:
> Why duzz ComplexExpand[Conjugate[ExpIntegralEi[I x/a]]] gives
> terms like -I Conjugate[x]/Conjugate[a] rather then -I x/a , where I
> is
> the imaginary....Help says that ComplexExpand assumes all variables are
> real...
>
> thanks....jerry blimbaum NSWC Panama City, Fl
>
>
>