Re: Can't solve Diff Equ
- To: mathgroup at smc.vnet.net
- Subject: [mg42769] Re: Can't solve Diff Equ
- From: "Bill Bertram" <wkb at ansto.gov.au>
- Date: Fri, 25 Jul 2003 05:08:17 -0400 (EDT)
- Organization: Australian Nuclear Science and Technology Organisation
- References: <bfo4ca$cbk$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
"Oliver Friedrich" <oliver.friedrich at tzm.de> wrote in message news:bfo4ca$cbk$1 at smc.vnet.net... > Hallo, > > I try to solve the following differential equation: > > equ=D[x[t], {t, 2}] == D[c[x], {x, 1}] D[x[t], {t, 1}] > > DSolve[equ,x[t],t] > > Mathematica 4.2 returns it unsolved. > > 1. Does DSolve need any more information ? > No, but you need to tell it that the "x" in your c[x] is really x[t]. So if you write instead, equ=D[x[t], {t, 2}] == D[c[x[t]], {x[t], 1}] D[x[t], {t, 1}], DSolve will return a result involving the unspecified function c plus two arbitrary constants. Cheers, Bill