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ParametricPlot Problem


Hi,

I'm trying to do a Parametric Plot of a 2nd order differential
equation:

1. dee = x''[t] + 0.5 x'[t] + x[t] + 0.1 x[t]^2 == Sin[0.1t];
2. constraints = { x[0] == 1, x'[0] == 0};
3. sol = NDSolve[ {dee, constraints}, x[t], {t, 0, 400} ];
4. ParametricPlot[  {Evaluate[ x[t] /. sol], y [t]}, {t, 0, 200}]

but it keeps telling me
"ParametricPlot::pptr: "\!\({Evaluate[x[t] /. \[InvisibleSpace]sol]}\)
does \
not evaluate to a pair of real numbers at t = 8.333333333333334`*^-6."
etc.

This is despite the fact that it works if I do a straight "Plot" (ie, I
just remove the "Parametric" part of 4.)

If anyone can suggest how I might correct this problem I would
appreciate it a lot since I'm quite out of ideas.

Thanks,

James
--
Mathematica 5.0
UK


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