Re: complex analysis problem in mathematica 3.0

*To*: mathgroup at smc.vnet.net*Subject*: [mg48470] Re: complex analysis problem in mathematica 3.0*From*: Paul Abbott <paul at physics.uwa.edu.au>*Date*: Tue, 1 Jun 2004 03:02:46 -0400 (EDT)*Organization*: The University of Western Australia*References*: <c9ec75$g9q$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

In article <c9ec75$g9q$1 at smc.vnet.net>, BranasMan <branasREmoVe at mail.inet.hr> wrote: > i have a complex function: > > H(s)=1 / (s^3 + 2s^2 + 2s + 1) > > whan i replace "s" with j*w (j=sqrt(-1)) i get: > > H=1 / (1 + j2w -2w^2 - jw^3) > > i would like to get that function in shape of : > H=something + j*something_else i.e. the complex > and real part apart. > > i played with Re and Im,but it seems that the fact that > "w" is a variable confuses mathematica?! For your function, h[s_] = 1/(s^3 + 2s^2 + 2s + 1); You can obtain the real and imaginary parts as follows: Simplify @ ComplexExpand @ Through @ {Re, Im} @ h[I w] Cheers, Paul -- Paul Abbott Phone: +61 8 9380 2734 School of Physics, M013 Fax: +61 8 9380 1014 The University of Western Australia (CRICOS Provider No 00126G) 35 Stirling Highway Crawley WA 6009 mailto:paul at physics.uwa.edu.au AUSTRALIA http://physics.uwa.edu.au/~paul