Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.soft-sys.math.mathematica > #3161 > unrolled thread

Re: Problems with DSolve

Back to article view | Back to comp.soft-sys.math.mathematica

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  Re: Problems with DSolve michael partensky <partensky@gmail.com> - 2011-06-17 09:52 +0000

#3161 — Re: Problems with DSolve

Your equations are incorrect; there is no equal (==) sign.
This is kind  like  asking Mathematica to solve x-2 instead of x-2 ==0.

On Thu, Jun 16, 2011 at 4:01 AM, David King <drdavidbking@gmail.com> wrote:

> Hello Mathematica Forum,
>
> I am a new forum contributer, so it is nice to meet you.  I was hoping
> at least one of you could help me out.  I am attempting to find an
> exact solution to a system of differential equations
>
> I  type in the following Dsolve  function:
>
>  sol=DSolve[{x'[t] -(0.355+(0.645t/(t+223.06)))x[t]+0.311y[t]
> +0.046z[t] - 0.149x[t] -0.259x[t],y'[t] 0.149x[t] -
> 0.311y[t],z'[t] 0.259x[t] -0.046z[t],x[0] D,y[0] 0,z[0] 0},
> {x[t],y[t],z[t]},t]
>
> So far, Mathematica  returns the following:
>
> Out[7]:=  DSolve[{x=A2[t] -0.408 x[t]+(-0.355-(0.645 t)/(223.06 +t)) x[t]
> +0.311 y[t]+0.046 z[t],y=A2[t] 0.149 x[t]-0.311 y[t],z=A2[t] 0.259
> x[t]-0.046 z[t],x[0] D,y[0] 0,z[0] 0},{x[t],y[t],z[t]},t]
>
> Which is what my question is.... This is kind of like asking  "Who's on
> first?"  and mathematica answers:  "Who's on first."  Which is what my
> question is....  I am pretty sure that my syntax is correct.  Anyway,
> I was hoping that you might be able to knock this one out of the
> park.
>
> I have a numerical solution, just not an exact solution.
>
>

[toc] | [standalone]

Back to top | Article view | comp.soft-sys.math.mathematica

csiph-web