Re: function
- To: mathgroup at smc.vnet.net
- Subject: [mg105975] Re: function
- From: Bill Rowe <readnews at sbcglobal.net>
- Date: Tue, 29 Dec 2009 01:17:14 -0500 (EST)
On 12/28/09 at 4:55 AM, fabian.uriarte at gmail.com (Fabian) wrote:
>Why can't Mathematica evaluate "Re[]" here ?
>{Rm, Xm} \[Element] Reals;
This suggests you have the impression that this would make Rm,
and Xm real for the rest of your notebook. That simply isn't so.
In fact, the expression above has no effect on your subsequent expressions.
>Z = (Rm*\[ImaginaryJ] Xm)/(Rm + \[ImaginaryJ]*Xm);
>Z = ComplexExpand[Z]
>Re[Z]
Since you want to extract the real portion of Z you need not set
Z to the results of ComplexExpand instead simply do
ComplexExpand[Re[Z]], that is:
In[1]:= Z = (I*Rm*Xm)/(Rm + I*Xm);
ComplexExpand[Re[Z]]
Out[2]= (Rm Xm^2)/(Rm^2+Xm^2)