Re: problems with DSolve

*To*: mathgroup at smc.vnet.net*Subject*: [mg99428] Re: problems with DSolve*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Tue, 5 May 2009 06:01:52 -0400 (EDT)*Organization*: Uni Leipzig*References*: <gtnk4s$3md$1@smc.vnet.net>*Reply-to*: kuska at informatik.uni-leipzig.de

Hi, may be that Plot[Evaluate[ (x[t] /. DSolve[{x'[t] == y[t], y'[t] == -x[t], x[0] == 1, y[0]== 2}], {x, y}, t]), {t, 0, 5}] will work too. Plot[] hat the attribute HoldAll. Regards Jens szymon.stoma at gmail.com wrote: > hello, > > i am new to mathematica, therefore sorry if my question is trivial. I > would like to understand why the following line does not work: > > Plot[(x[t] /. DSolve[{x'[t] == y[t], y'[t] == -x[t], x[0] == 1, y[0] > == 2}, {x, y}, t]), {t, 0, 5}] > > whereas after splitting into two lines it works: > sol = DSolve[{x'[t] == y[t], y'[t] == -x[t], x[0] == 1, y[0] == 2}, > {x, y}, t] > Plot[(x[t] /. sol), {t, 0, 5}] > > i would like to use Manipulate to play with boundary conditions, so > the first notation would be highly useful. > > thanks a lot for any feedback. >