Re: What's DSolve's output when it cant find a solution ?

• To: mathgroup at smc.vnet.net
• Subject: [mg87205] Re: What's DSolve's output when it cant find a solution ?
• From: Szabolcs Horvát <szhorvat at gmail.com>
• Date: Fri, 4 Apr 2008 02:56:57 -0500 (EST)
• Organization: University of Bergen
• References: <ft2anu\$paq\$1@smc.vnet.net>

```zerodynamics at gmail.com wrote:
> Im using Mathematica 6 to look for solutions to a system of nonlinear ODE's. I
> don't
> expect a solution, but the only output Im getting is an exact reprint
> of my input.
> This usually means that the arguments to the function are incorrect,
> but Im
> fairly certain they're OK.
>
> Here is my input:
>
> In[11]:=   Dsolve[{s''[t] + Cot[u[t]/2]*s'[t]*u'[t] ==  0,   u''[t] -
> Sin[u[t]]*s'[t]^2 == 0 }, {s[t], u[t]}, t]
> Out[11]:= Dsolve[{s''[t] + Cot[u[t]/2]*s'[t]*u'[t] ==  0,   u''[t] -
> Sin[u[t]]*s'[t]^2 == 0 }, {s[t], u[t]}, t]
>
> Is this what I should expect when DSolve can't find a solution ? Also,
> this is returned immediately
> without any "Running ... ".

Yes, when DSolve returns unevaluated, it cannot solve the equation.  You
misspelled DSolve as Dsolve above, but Mathematica still cannot solve
this equation.

```

• Prev by Date: Re: What's DSolve's output when it cant find a solution ?
• Next by Date: Re: What is @@@?
• Previous by thread: Re: What's DSolve's output when it cant find a solution ?
• Next by thread: Re: Colorfunction based upon flux direction