Re: Question for using complex variables

• To: mathgroup at smc.vnet.net
• Subject: [mg13726] Re: Question for using complex variables
• From: Paul Abbott <paul at physics.uwa.edu.au>
• Date: Wed, 19 Aug 1998 01:38:18 -0400
• Organization: University of Western Australia
• References: <6r10kv\$fjg@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Chongdae Park wrote:

> Here, x, y, w, and z are all real values. Then I expected
>
> Complex[x,y]*Complex[w,z]=(xw-yz)+I(xz+yw)

First, note that

In[1]:= ?Complex
"Complex is the head used for complex numbers."

so, to work with complex variables in explicit form, you should not use
Complex but instead enter them directly as x+I y, etc.

Second, ComplexExpand is the operator you want for simplifying complex
expressions (assuming that the variables x,y,w,z are real):

In[2]:= ComplexExpand[(x + I y) (w + I z)]
Out[2]= w x - y z + I (w y + x z)

Cheers,
Paul

____________________________________________________________________
Paul Abbott                                   Phone: +61-8-9380-2734
Department of Physics                           Fax: +61-8-9380-1014
The University of Western Australia            Nedlands WA  6907
mailto:paul at physics.uwa.edu.au  AUSTRALIA
http://www.physics.uwa.edu.au/~paul

God IS a weakly left-handed dice player
____________________________________________________________________

```

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