Re: 2 coupled diff. eqns
- To: mathgroup at smc.vnet.net
- Subject: [mg21178] Re: 2 coupled diff. eqns
- From: "Kevin J. McCann" <kevin.mccann at jhuapl.edu>
- Date: Fri, 17 Dec 1999 01:23:09 -0500 (EST)
- Organization: Johns Hopkins University Applied Physics Lab, Laurel, MD, USA
- References: <831vap$g58@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
The "\)" in your DSolve call should not be there, but, unfortunately, DSolve still doesn't solve it, but takes a long time to figure it out (~3 min). Kevin -- Kevin J. McCann Johns Hopkins University APL Henk Jansen <hj at rdr-nl.com> wrote in message news:831vap$g58 at smc.vnet.net... > I have the following set of two coupled differential equations: > > c f > f' = a - ---------------- > ___________ > \ / 2 2 > \/ f + g > > c g > g' = b - ---------------- > ___________ > \ / 2 2 > \/ f + g > > > where a, b and c are constants. Trying to solve this system (if > possible), after typing > > DSolve[ > {D[f[t], t] == a - (w f[t])/(Sqrt[f[t]^2 + g[t]^2])\), > D[g[t], t] == b - (w g[t])/(Sqrt[f[t]^2 + g[t]^2])\) > }, > {f[t], g[t]}, > t] > > Mathematica returns with the following message: > > "Part::partw: Part 2 of g'[f] does not exist." > > without solution. I have two questions: > > 1. Does anyone know how to interprete this message? > > 2. If the system is not solvable, is there a clever coordinate > transformation for which the system can be solved? > > Thanks, > > Henk Jansen > > -- > = = Henk Jansen ======== H.Jansen at fel.tno.nl = = > = == TNO Physics and Electronics Laboratory == = > = ==== PO Box 96864 === 2509 JG The Hague ==== = > = ============= The Netherlands ============== = > = Phone: +31 70 374 0215 Fax: +31 70 374 0654 = > = ============================================ > ---------------------------------------- > > > Sent via Deja.com http://www.deja.com/ > Before you buy. >