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.