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

  • To: mathgroup at smc.vnet.net
  • Subject: [mg116015] Re: Initial condition with DSolve in Mathematica 8 doesn't work
  • From: "Nasser M. Abbasi" <nma at 12000.org>
  • Date: Sat, 29 Jan 2011 05:26:42 -0500 (EST)
  • References: <ihu8f1$1lc$1@smc.vnet.net>
  • Reply-to: nma at 12000.org

On 1/28/2011 3:14 AM, Bert RAM Aerts 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?
>

It works here:

In[4]:= $Version
8.0 for Microsoft Windows (64-bit) (November 13, 2010)


In[6]:= DSolve[{y'[x]+y[x]==a Sin[x],y[0]==0},y[x],x]
Out[6]= {{y[x]->-(1/2) a E^-x (-1+E^x Cos[x]-E^x Sin[x])}}


May be you can post the InputForm? may be your ' is not really a '  ?

--Nasser


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