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MathGroup Archive 2000

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Re: newbie PolarPlot question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg25070] Re: [mg25046] newbie PolarPlot question
  • From: BobHanlon at aol.com
  • Date: Thu, 7 Sep 2000 22:28:13 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 9/3/2000 10:22:37 PM, dmagnoli at home.com writes:

>I've defined:
>
>r[t] := 16/(5 + 3 Cos[t])
>
>Then I load Graphics, with:
>
><<Graphics`
>
>and ask for:
>
>PolarPlot[r, {t, 0, 2 Pi}], which tells me:
>
>ParametricPlot::pptr:
>{r Cos[t], r Sin[t]} does not evaluate to a pair
>of real numbers at t = 2.617993877991494`*^-7
>
>ParametricPlot::pptr:
>{r Cos[t], r Sin[t]} does not evaluate to a pair
>of real numbers at t = 0.25488992540742256`.
>
>ParametricPlot::pptr:
>{r Cos[t], r Sin[t]} does not evaluate to a pair
>of real numbers at t = 0.5328694051959509`.
>
>General::stop:
>Further output of ParametricPlot ::pptr will be
>suppressed during this calculation.
>
>Near as I can make out, x and y should both evaluate to real numbers for
>any value of theta between 0 and 2 Pi, so I don't know what I'm doing
>wrong.
>

Needs["Graphics`Graphics`"];

The function definition should read:

r[t_] := 16/(5 + 3 Cos[t]);

The plot call should read:

PolarPlot[r[t], {t, 0, 2 Pi}];


Bob Hanlon


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