Re: DSolve to solve simultaneous ODEs
- To: mathgroup at smc.vnet.net
- Subject: [mg9472] Re: [mg9443] DSolve to solve simultaneous ODEs
- From: "W. Meeussen" <w.meeussen.vdmcc at vandemoortele.be>
- Date: Thu, 6 Nov 1997 02:40:15 -0500
- Sender: owner-wri-mathgroup at wolfram.com
hi,
I get with Mathematica 3.0.0.0:
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[t],p[t],s[t]},t]//
InputForm
{{x[t] -> (E^(t*u)*m)/(E^(t*u) - E^C[3]), p[t] -> (u*C[1] +
m*n*Log[-E^(t*u) +
E^C[3]])/u,
s[t] -> (-(E^C[3]*m*u*Yp) + E^(t*u)*u*Yp*Yx*C[2] -
E^C[3]*u*Yp*Yx*C[2] -
E^(t*u)*m*n*Yx*Log[-E^(t*u) + E^C[3]] +
E^C[3]*m*n*Yx*Log[-E^(t*u) + E^ C[3]])/
((E^(t*u) - E^C[3])*u*Yp*Yx)}}
seems upgrading to 3.0 pays off ...
wouter.
At 01:57 5-11-97 -0500, 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
>
>
>
Dr. Wouter L. J. MEEUSSEN
w.meeussen.vdmcc at vandemoortele.be
eu000949 at pophost.eunet.be