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MathGroup Archive 1999

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Re: Manipulating differential equations

  • To: mathgroup at smc.vnet.net
  • Subject: [mg18622] Re: Manipulating differential equations
  • From: smudge at world.std.com (smudge)
  • Date: Tue, 13 Jul 1999 01:01:39 -0400
  • Organization: The World Public Access UNIX, Brookline, MA
  • References: <7m6jti$2mc@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Martin Heimann (martin.heimann at bgc-jena.mpg.de) 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?

Try the following

   dg1 /. c -> (Exp[-a #]&)




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