
Re: How to get the Real and Imaginary part of an expression
Posted:
Jan 5, 2013 2:17 AM


expr = (w = 882)/(s^2 + 2*z*w*s + w^2);
re = Re[ComplexExpand[expr, s]] // Simplify[#, Element[z, Reals]] &;
im = Im[ComplexExpand[expr, s]] // Simplify[#, Element[z, Reals]] &;
expr == re + I*im // FullSimplify
True
Using a concrete example
s2 = RandomComplex[] // Rationalize[#, 0] &;
re2 = re /. s > s2 // Simplify[#, Element[z, Reals]] &;
im2 = im /. s > s2 // Simplify[#, Element[z, Reals]] &;
(expr /. s > s2) == re2 + I*im2 // Simplify
True
Bob Hanlon
On Wed, Jan 2, 2013 at 9:16 PM, Eduardo M. A. M. Mendes <emammendes@gmail.com> wrote: > Hello > > I need to extract the real and imaginary part of the following expression > > (w=882)/(s^2+2*z*w*s+w^2) > > where w and z are positive constants. s is a complex variable. > > Applying Re and Im to the expression does not do much. By hand, one can easily find them. > > What am I missing? > > many thanks > > Ed > > >

