Mathematica real part

The Wolfram Language has fundamental support for both explicit complex numbers and symbolic complex variables. All applicable mathematical functions support arbitrary-precision evaluation for complex values of all parameters, and symbolic operations automatically treat complex variables with full generality.

x+Iy— the complex number

I () — (entered as ii "imaginary ", or jj)

Complex— convert a pair of reals to a complex number

Re— real part

Im— imaginary part

ReIm— the list

Abs— absolute value

Arg— argument (phase angle in radians)

AbsArg— the list {,arg(z)}

Sign— normalized direction ()

Conjugate— complex conjugate (also entered with superscript co)

ConjugateTranspose— Hermitian conjugate of a matrix (also entered with ct)

ComplexExpand— expand symbolic expressions into real and imaginary parts

PowerExpand— expand symbolic expressions ignoring branch cuts

ExpToTrig, TrigToExp— convert between complex exponentials and trig functions

GaussianIntegers— option for polynomial and number theory functions

Reduce— reduce equations and inequalities over complex numbers

RandomComplex— random complex number

I have a complex expression with real positive variables only.

Mathematica Input Style:

which leads to

$ PP=-\frac{i \sqrt{-\frac{i \omega }{d}} \left(\frac{(\text{kd}-i \omega ) \text{Cosh}\left[\text{y1} \sqrt{-\frac{i \omega }{d}}\right]}{\text{ka}}+\sqrt{-\frac{i \omega }{d}} \text{Sinh}\left[\text{y1} \sqrt{-\frac{i \omega }{d}}\right]\right) \left(-\frac{(\text{kd}-i \omega ) \text{Cosh}\left[(-L+\text{y2}) \sqrt{-\frac{i \omega }{d}}\right]}{\text{ka}}+\sqrt{-\frac{i \omega }{d}} \text{Sinh}\left[(-L+\text{y2}) \sqrt{-\frac{i \omega }{d}}\right]\right)}{\omega \left(\frac{2 (\text{kd}-i \omega ) \sqrt{-\frac{i \omega }{d}} \text{Cosh}\left[L \sqrt{-\frac{i \omega }{d}}\right]}{\text{ka}}+\left(\frac{(\text{kd}-i \omega )^2}{\text{ka}^2}-\frac{i \omega }{d}\right) \text{Sinh}\left[L \sqrt{-\frac{i \omega }{d}}\right]\right)} $

Now I want to extract the real part of this by assuming real only variables and then . Mathematica 8 can't extract it.

I saw on different forums that many people have had difficulties with extracting real or imaginary parts of expressions with built-in .

Some propose to replace by , which seems to work well in some cases. Do you have other suggestions?

All the variables are real and positive, so that I define at the beginning of my Mathematica notebook:

My version of Mathematica is

asked Mar 21 '12 at 10:48