Re: Real and Imaginary Parts of complex functions

*To*: mathgroup at smc.vnet.net*Subject*: [mg129944] Re: Real and Imaginary Parts of complex functions*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Wed, 27 Feb 2013 03:07:58 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net*References*: <20130226060933.C3A19687D@smc.vnet.net>

Did you try a search in the Documentation Center? If you do, one of the things you'll find near the top of the hits is Complex Numbers (Mathematica Guide) which includes a list of functions. One of these is: ComplexExpand - expand symbolic expressions into real and imaginary parts Then look at the reference page for that; it's what you want here. ComplexExpand[Re[1/(x + y I)]] x/(x^2 + y^2) The Refine and the assumptions about x and y are superfluous: the whole point of ComplexExpand is that it assumes symbolic variables used within it are already real. On Feb 26, 2013, at 1:09 AM, Brentt <brenttnewman at gmail.com> wrote: > > Hello, > > 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? > --- Murray Eisenberg murray at math.umass.edu Mathematics & Statistics Dept. Lederle Graduate Research Tower phone 413 549-1020 (H) University of Massachusetts 413 545-2838 (W) 710 North Pleasant Street fax 413 545-1801 Amherst, MA 01003-9305

**References**:**Real and Imaginary Parts of complex functions***From:*Brentt <brenttnewman@gmail.com>