       Re: How to rectify the error for NDSolve ?

• To: mathgroup at smc.vnet.net
• Subject: [mg127128] Re: How to rectify the error for NDSolve ?
• From: Rahul Chakraborty <rahul.6sept at gmail.com>
• Date: Sun, 1 Jul 2012 02:11:59 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com

```Here is my code:

clear[x, t, \[Tau], Q, Subscript[V, p], Subscript[V,
1], \[CapitalGamma], \[Phi]];
Q = 100;
\[CapitalGamma] = 50;
Subscript[\[Omega], 0] = 10;
Subscript[V, p] = 0.5;
Subscript[C, 0] = 4.06 * 10^-4;
t = 5;
\[Tau] = Subscript[\[Omega], 0] t;
\[Phi] = 90;
Subscript[V, 1] = Subscript[C, 0]*Subscript[V, p];
eqn = x'' (\[Tau]) +
1/Q x' (\[Tau]) + (1 +
Subscript[V, 1] Sqrt
Sin[2 \[Tau]]) x == \[CapitalGamma] (sin[\[Tau] + \[Phi]]);
sol = NDSolve[{eqn, x == 0.5, x' == 0}, x, {t, 0, 250},
MaxSteps -> 500000, WorkingPrecision -> 25][]
ParametricPlot[Evaluate[{x[t], x'[t]} /. sol], {t, 0, 100},
Frame -> True, PlotRange -> All,
AxesLabel -> {"t", "\!\(\*OverscriptBox[\(\[Theta]\), \(.\)]\)"}]

Output i'm getting is as below:

NDSolve::dsvar: 5 cannot be used as a variable. >>

{0.999855 x + Derivative[x]/2 + 50 x^\[Prime]\[Prime] ==
50 sin, x == 0.5, Derivative[x] == 0}

ReplaceAll::reps: {0.999855 x+x^\[Prime]/2+50 x^\[Prime]\[Prime]==50 sin,x==0.5,(x^\[Prime])==0} is neither a list of replacement rules nor a valid dispatch table, and so cannot be used for replacing. >>

ReplaceAll::reps: {0.999855 x+0.5 x^\[Prime]+50. x^\[Prime]\[Prime]==50. sin[140.],x[0.]==0.5,(x^\[Prime])[0.]==0.} is neither a list of replacement rules nor a valid dispatch table, and so cannot be used for replacing. >>

ReplaceAll::reps: {0.999855 x+0.5 x^\[Prime]+50. x^\[Prime]\[Prime]==50. sin[140.],x[0.]==0.5,(x^\[Prime])[0.]==0.} is neither a list of replacement rules nor a valid dispatch table, and so cannot be used for replacing. >>

General::stop: Further output of ReplaceAll::reps will be suppressed during this calculation. >>

Regards,

rahul

```

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