Re: Manipulating differential equations
- To: mathgroup at smc.vnet.net
- Subject: [mg18640] Re: Manipulating differential equations
- From: Eckhard Hennig <hennig at itwm.uni-kl.de>
- Date: Thu, 15 Jul 1999 01:45:37 -0400
- Organization: ITWM
- References: <7m6jti$2mc@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
>I would like to insert test functions into an expression that contains
>differentials:
>
>dg1 = c''[x] + g c'[x]
>
>I would like e.g. to replace c[x] by Exp[-a x]:
>
>dg1/.c[x]->Exp[-a x]
>
>but this doesn't work; one has to put substitution rules for each of the
>derivatives explicitly. Is there a more elegant way to achieve this?
In[1]:= dg1 = c''[x] + g c'[x];
In[2]:= dg1 /. c -> (Exp[-a #]&)
Out[2]=
2
a a g
-------- - --------
-(-a x) -(-a x)
E E
-- Eckhard
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Dipl.-Ing. Eckhard Hennig mailto:hennig at itwm.uni-kl.de
Institut fuer Techno- und Wirtschaftsmathematik e.V. (ITWM)
Erwin-Schroedinger-Strasse, 67663 Kaiserslautern, Germany
Voice: +49-(0)631-205-3126 Fax: +49-(0)631-205-4139
http://www.itwm.uni-kl.de/as/employees/hennig.html
ITWM - Makers of Analog Insydes for Mathematica
http://www.itwm.uni-kl.de/as/products/ai
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