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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


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