Re: function manipulation

• To: mathgroup at smc.vnet.net
• Subject: [mg127831] Re: function manipulation
• From: Bob Hanlon <hanlonr357 at gmail.com>
• Date: Sat, 25 Aug 2012 04:26:01 -0400 (EDT)
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• References: <20120824005115.06CE5687C@smc.vnet.net>

```gl2 = Module[
{eqn, z = Subscript[\[Tau], xy]''[x], coef},
eqn = Subscript[g,
K] (Subscript[e, 1] Subscript[t, 1] +
Subscript[e, 2] Subscript[t, 2]) Subscript[\[Tau], xy][x] ==
Subscript[e, 1] Subscript[e, 2] Subscript[t, 1] Subscript[t, 2]
Subscript[t, K] (Subscript[\[Tau], xy]^\[Prime]\[Prime])[x];
(z /. Solve[eqn, z][[1]]) - z == 0];

{gl3, repl} = Module[
{coef = Coefficient[gl2[[1]], Subscript[\[Tau], xy][x]]},
{gl2 /. Numerator[coef] ->
\[Omega]^2*Denominator[coef],
\[Omega] -> Sqrt[coef]}];

gl3

\[Omega]^2*Subscript[\[Tau], xy][x] -
Derivative[2][Subscript[
\[Tau], xy]][x] == 0

(gl3 /. repl) === gl2

True

Bob Hanlon

On Fri, Aug 24, 2012 at 6:39 AM, Andreas Talmon l'Arm=E9e
<talmon at fsm.tu-darmstadt.de> wrote:
> Hi
>
> Thanks, this did exactly the job. But unfortunately I got another issue. I
> wanted to replace the fraction by the parameter omega^2 in gl3. So far it
> worked well. But then I tried to define omega for further calculations. At
> the end it did not matter if I solved gl2 or gl3 with DSolve. omega^2 was
> always replaced by its definition. Can I force mathematica to use the much
> shorter parameter omega^2 for a clear arrangement. I attached the file where
> I tried to do the calculation :
>
> Best regards Andreas Talmon
>
>
>

```

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