re: COMPLEXEXPAND
- To: mathgroup at smc.vnet.net
- Subject: [mg22588] re: [mg22564] COMPLEXEXPAND
- From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
- Date: Sun, 12 Mar 2000 22:55:32 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
On Saturday, March 11, 2000 11:52:39 PM, Blimbaum Jerry DLPC wrote:
> I am trying to get some results expressed in the form Abs[x] Exp[I
> theta].
>
> So, if I type in
> ComplexExpand[z,{z},TargetFunctions->{Abs,Arg}]//TrigToExp I get
> Abs[z] Exp[I Arg[z]] which is what I want,
>
> but if I type in ComplexExpand[x+ I y, TargetFunctions->{Abs,
> Arg}]//TrigToExp I just get back x + I y.
>
> Would someone explain this to me. I was expecting the output
> Sqrt[x^2+y^2] Exp[I ArcTan[x,y]]
>
> Since my results are in the form x + I y, the Mathematica output
> doesnt do me any good.
>
> thanks. jerry blimbaum
>
>
The reason why ComplexExpand does nothing is that from Mathematica's point
of view an expression like x+y*I is already as "fully expanded" so there
nothing to do here. In such cases the simplest thing to do is to write your
own function which does what you want, e.g.:
In[24]:=
myComplexExpand[z_] :=
ComplexExpand[Abs[z], TargetFunctions -> {Re, Im}]*
Exp[I*ComplexExpand[Arg[z], TargetFunctions -> {Re, Im}]]
In[25]:=
myComplexExpand[a + b*I]
Out[25]=
2 2 I ArcTan[a, b]
Sqrt[a + b ] E
and
In[26]:=
myComplexExpand[2 + 3*I]
Out[26]=
I ArcTan[3/2]
Sqrt[13] E
--
Andrzej Kozlowski
Toyama International University
JAPAN
http://sigma.tuins.ac.jp