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MathGroup Archive 2001

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Re: 2nd order differential equation help

  • To: mathgroup at smc.vnet.net
  • Subject: [mg31481] Re: 2nd order differential equation help
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Thu, 8 Nov 2001 04:54:15 -0500 (EST)
  • Organization: Universitaet Leipzig
  • References: <9sb4rb$h1n$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hmm,

a second order equation needs two initial conditions ?
What is your eqn1[t_] doing ?

DSolve[{g''[t] + 0.1g'[t] + g[t] == 0,
        g'[0]==1,
        g[0]==0},
       g[t]
      ]

Regards
  Jens

Peter Dimitriou wrote:
> 
> Exactly how do I get this into a form Mathamatica will accept?  It has
> been a number of years since enrolling in diffeq, however I think I am
> close to correct but would appreciate help.
> 
> the problem;
> 
> Solve the differential equation:
> 
> g''(t) + 0.1 g'(t) + g(t) = 0
> 
> where the previous equation uses conventional mathematical notation.
> You must transfrom the equation and initial conditions into
> Mathematica syntax.
> 
> for t between 0 and 10 Pi
> 
> subject to the initial conditions
>         g(0) = 0,
>         g'(0) = 1
> 
> Plot your results.
> 
> My attempt is as follows:
> 
> Clear[g]
> 
> Clear[eqn]
> 
> eqn[t_] = g''[t] + 0.1g'[t] + g[t] == 0
> 
> Clear[eqn1]
> 
> eqn1[t_] = g'[t] + 0.1g[t] + ?g[t] == 0
> 
> solution = DSolve[{eqn[t], eqn1[t]}, g'[0] == 1,
> g[0] == 0, g[t], {t, 0, 10\[Pi]}]
> 
> DSolve::dsvar: g[0]==0 cannot be used as a variable.
> 
> what am I dont doing right?  any suggestions helpful


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