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Re: Problem with ->

To: mathgroup@smc.vnet.net
Subject: [mg11472] Re: Problem with ->
From: Allan Hayes <hay@haystack.demon.co.uk>
Date: Thu, 12 Mar 1998 01:34:59 -0500
References: <6dv2lm$5dl@smc.vnet.net>

Hans Steffani wrote:
> 
> I want to substitute R[s] by k s.
> I tried:
> R[s] / R'[s] /. R[s] -> k s
> and got
> k s / R'[s]
> instead of the expected
> s
> 
> What am I doing wrong?
> 
> Hans Friedrich Steffani
> --
> Hans Friedrich Steffani
> Institut fuer Elektrische Maschinen und Antriebe, TU Chemnitz
> mailto:hans.steffani@e-technik.tu-chemnitz.de
> http://www.tu-chemnitz.de/~hfst/

Hans,

FullForm[R'[s]]

Derivative[1][R][s]

So we need to regard R as a function

R[s] / R'[s] /. R ->( k#& )

s

Allan
-- 
Allan Hayes
Mathematica Training and Consulting
Leicester, UK
hay@haystack.demon.co.uk
http://www.haystack.demon.co.uk
voice: +44 (0)116 271 4198
fax: +44 (0)116 271 8642

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