Re: Manipulating differential equations
- To: mathgroup at smc.vnet.net
- Subject: [mg18593] Re: [mg18552] Manipulating differential equations
- From: BobHanlon at aol.com
- Date: Tue, 13 Jul 1999 01:01:26 -0400
- Sender: owner-wri-mathgroup at wolfram.com
Martin, dg1 = c''[x] + g c'[x]; dg1 /. NestList[D[#, x] &, c[x] -> Exp[-a*x], 2] // Simplify (a*(a - g))/E^(a*x) Bob Hanlon In a message dated 7/10/99 7:16:39 AM, martin.heimann at bgc-jena.mpg.de writes: >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? >