Re: DSolve to solve simultaneous ODEs
- To: mathgroup at smc.vnet.net
- Subject: [mg9485] Re: DSolve to solve simultaneous ODEs
- From: Wojciech Budzianowski <wbudzian at iic.pwr.wroc.pl>
- Date: Sat, 8 Nov 1997 23:04:19 -0500
- Organization: I-13 PWr
- Sender: owner-wri-mathgroup at wolfram.com
Kelvin Yip wrote:
>
> Hi Everyone,
>
> Although I follow closely the Mathematica book's instruction , I still
> only receive a out put which is just a parapharse of my input. The
> Program (Version 2.2) work well on solving single equation but not a
> systems of ODEs, anyone can help ?
>
> DSolve[(u*x[t]*(1-x[t]/xmax)-x'[t]==0),x[t],t]
> t u
> E
> {{x[t] -> -----------}, {x[t] -> 0}}
> t u
> E
> ---- + C[1]
> xmax
>
> This one is OK but not the one below!
>
> DSolve[{(u*x[t]*(1-x[t]/m)-x'[t]==0),
> (n*x[t]-p'[t]==0),(-p'[t]/Yp-x'[t]/Yx-s'[t]==0)},{x,p,s},t]
> x[t]
> DSolve[{u x[t] (1 - ----) - x'[t] == 0, n x[t] - p'[t] == 0,
> m
>
> p'[t] x'[t]
> -(-----) - s'[t] - ----- == 0}, {x, p, s}, t]
> Yp Yx
>
> I have tried to load the DSolve package first then type my equation in,
> still no success.
>
> Thank you for your attention!
>
> Kelvin Yip
Your ODE could be simplified to:
s'[t]==(-n/Yp-u)*x[t]+(u/m)*x[t]*x[t] Try
Integrate[(-n/Yp-u)*x[t]+(u/m)*x[t]*x[t],x] Maybe that would help
Best regards
--
---------------------------------------------------- Wojciech
Budzianowski
wbudzian at iic.pwr.wroc.pl
http://www.iic.pwr.wroc.pl/~wbudzian Phone Work +48 +71 3203625
Institute of Chemical Engineering and Heat Equipment Wroclaw University
of Technology
Wroclaw, Poland
Norwida 4/6 50-373 Wroclaw
----------------------------------------------------