Re: Initial condition with DSolve in Mathematica 8 doesn't work

*To*: mathgroup at smc.vnet.net*Subject*: [mg116036] Re: Initial condition with DSolve in Mathematica 8 doesn't work*From*: Helen Read <readhpr at gmail.com>*Date*: Sat, 29 Jan 2011 19:42:49 -0500 (EST)*References*: <ihu8f1$1lc$1@smc.vnet.net> <ii0ps2$j25$1@smc.vnet.net>

On 1/29/2011 5:24 AM, Bert RAM Aerts wrote: > After restarting Mathematica 8.0.0 Home Edition (on Mandriva Linux > 2010.2 x86_64) the command suddenly started working just fine. > I have no clue why it at first did not work... > > > > On 28 jan, 12:14, Bert RAM Aerts<bert.ram.ae... at gmail.com> wrote: >> When I enter the following in Mathematica 8.0.0 Home Edition: >> DSolve[{y'[x] + y[x] == a Sin[x], y[0] == 0}, y[x], x] >> I get >> DSolve::deqn: Equation or list of equations expected instead of True >> in the first argument {y[x]+(y^\[Prime])[x]==a Sin[x],True}.>> >> >> The initial condition becomes a "True"... >> >> In Mathematica 7.0.1 Home Edition, this same input gives the expected >> output: >> {{y[x] -> -(1/2) a E^-x (-1 + E^x Cos[x] - E^x Sin[x])}} >> >> What am I missing? Most likely you originally had set y[0]=0 or something like that. Clear[y] would have fixed it. Quitting Mathematica clears everything, so that also fixed the problem. -- Helen Read University of Vermont