Re: Real and Imaginary Parts of complex functions

• To: mathgroup at smc.vnet.net
• Subject: [mg129936] Re: Real and Imaginary Parts of complex functions
• From: Bill Rowe <readnews at sbcglobal.net>
• Date: Wed, 27 Feb 2013 03:05:17 -0500 (EST)
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• Delivered-to: l-mathgroup@wolfram.com
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```On 2/26/13 at 1:09 AM, brenttnewman at gmail.com (Brentt) wrote:

>I was wondering why this works

>IN[]:= Refine[Re[x + y I], Element[x , Reals] && Element[y , Reals]]

>Out[]:= x

>But this does not

>In[]:= Refine[Re[1/(x + y I)], Element[x , Reals] && Element[y ,
>Reals]]

>Out[]:= Re[1/(x + y I)]

>Is there a nice built in way to get the real and imaginary parts of
>a complex function?

ComplexExpand, for example:

In[3]:= List @@ ComplexExpand[1/(x + y I)]

Out[3]= {x/(x^2 + y^2), -((I*y)/(x^2 + y^2))}

```

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