Re: Manipulating differential equations
- To: mathgroup at smc.vnet.net
- Subject: [mg18651] Re: Manipulating differential equations
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Thu, 15 Jul 1999 01:45:44 -0400
- Organization: Universitaet Leipzig
- References: <7m6jti$2mc@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
try
dg1 /. Thread[{#,D[#,x],D[#,x,x]} & /@ (c[x]->Exp[-a x])]
Hope that helps
Jens
Martin Heimann wrote:
>
> Dear colleagues,
>
> 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?
>
> Cheers,
> Martin Heimann