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Re: Is this solvable using Mathematica?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg99075] Re: Is this solvable using Mathematica?
  • From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
  • Date: Sun, 26 Apr 2009 01:38:40 -0400 (EDT)
  • References: <gsuiqn$dq8$1@smc.vnet.net>

One problem is that d doesn't have a value...

On Apr 25, 10:49 am, johnboy98... at yahoo.com wrote:
> Supposed you want to define a second order derivative along with your
> ODEs. (So you can scale the second order term)
>
> Example shown below.
>
> k1 = 1;
> r1 = 1;
> NDSolve[{a'[t] == k1 b[t] - d, a''[t] == r1 b'[t], a'[0] == 0=
, a[0] ==
> 1, b[0] == 0}, {a[t], b[t]}, {t, 1, 10} ]
>
> But I get an error.
>
> NDSolve::ntdvmm:
> Cannot solve to find an explicit formula for the derivatives.  NDSolve
> will try solving the system using a mass matrix method.
>
> NDSolve::ndnum: Encountered non-numerical value for a derivative at t
> == 0.`.
>
> Maybe this is more of a math question than software. But I would be
> very interested in seeing if it's doable in Mathematica.
>
> Thanks in advance.



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