Re: Re: Can anyone help about this inverse laplacetransform problem?
- To: mathgroup at smc.vnet.net
- Subject: [mg33316] Re: [mg33279] Re: [mg33260] Can anyone help about this inverse laplacetransform problem?
- From: Sseziwa Mukasa <mukasa at jeol.com>
- Date: Thu, 14 Mar 2002 19:51:17 -0500 (EST)
- Organization: JEOL (USA) Ltd.
- References: <F100QADzBLwv16vFnlW00011145@hotmail.com>
- Sender: owner-wri-mathgroup at wolfram.com
david Xia wrote: > Thanks for your suggestion, since the expression of fi is a rational > expression, how to use mathematica to seperate fi into different parts > according to its poles? Is there a function to do this automatically? > {ToRules[Roots[Denominator[Together[f4s]]==0,s]]}should get you the roots as a list of replacement rules for s, the expression will be complicated. > > To find the poles, for my question, the parameters are all unknown > variables, will the find root routine find roots based on the symbolic > function? As I understand, the root function works only for numerical > solution by newton-raphson method given a initial value, am I right? If so, > then how to find root then for a symbolic function? > Roots is explicitly for finding all the roots of a polynomial expression. Since the denominator of the rational function is of fourth degree there is a closed form expression for the roots, but it is complicated. Regards, Ssezi