Re: What do I do to get better curves?

• To: mathgroup at smc.vnet.net
• Subject: [mg120943] Re: What do I do to get better curves?
• From: "Kevin J. McCann" <Kevin.McCann at umbc.edu>
• Date: Thu, 18 Aug 2011 03:22:41 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <j2g371\$1ek\$1@smc.vnet.net>

```Here is what you want, I think:

ContourPlot[Chop[a[k, w]] == 0, {w, 0, 6}, {k, 0, 3},
PlotRange -> All, PlotPoints -> 200, GridLines -> Automatic]

You can include more points to get the diagonal "boundary" better defined.

Kevin

On 8/17/2011 5:55 AM, becko wrote:
> Run the following code in mathematica:
>
> r=6197/3122;
> p[k_,w_]:=Sqrt[w^2/r^2-k^2];q[k_,w_]:=Sqrt[w^2-k^2];
> a[k_,w_,p_,q_]:=(k^2-w^2)^2 Sin[p]Cos[q]+4k^2 p q Cos[p]Sin[q]
> a[k_,w_]:=a[k,w,p[k,w],q[k,w]];
> ContourPlot[a[k,w]==0,{w,0,6},{k,0,14}]
>
> The curves thus obtained are very inaccurate. I tried raising the
> PlotPoints and WorkingPrecision opions of ContourPlot, but it doesn't
> work. Morevoer, you see that the only parameter that shows up, 'r', is
> an exact rational number. I don't know what else to try. Thanks.
>

```

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