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Re: PolarPlot

  • To: mathgroup at
  • Subject: [mg87613] Re: PolarPlot
  • From: dh <dh at>
  • Date: Mon, 14 Apr 2008 05:45:36 -0400 (EDT)
  • References: <ftmu5p$50d$>

Hi Bruce,

the radius in polar coordinates has to be real and positive. Therefore, 

r=Sqrt[Cos[phi]] can not be the correct formula, we would get imaginary 

values. To prevent this, we may e.g. write: r=Sqrt[Abs[Cos[phi]] what 

gives the plot you are looking for.

hope this helps, Daniel

Bruce Colletti wrote:

> Re 6.0.2 under WinXP.


> I'm using the command below to plot the polar equation r^2 = 4a^2 Cos@theta.  Is there a better way?  Thankx.


> Bruce


> PolarPlot[{2 a Sqrt[Cos@t], -2 a Sqrt[Cos@t]}, {t, 0, 2 \[Pi]}, 

>  PlotRange -> 7]


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