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Re: Polar Plot

  • To: mathgroup at smc.vnet.net
  • Subject: [mg82741] Re: Polar Plot
  • From: Peter Pein <petsie at dordos.net>
  • Date: Tue, 30 Oct 2007 03:29:17 -0500 (EST)
  • References: <fg4dhs$6dc$1@smc.vnet.net>

Miguel schrieb:
> How can I to plot a polar expresion in implicit form. For example,
> r^2==3+2*r*Cos[teta]
> 
> 
Hello Miguel,

in Version 5.2
In[1]:=
xy = Simplify[Expand[{x, y} /.
     {ToRules[Reduce[{r^2 == 3 + 2*r*Cos[t], x == r*Cos[t], y == r*Sin[t]},
        {t, r, x, y}, Backsubstitution -> True]]}]]
Out[1]=
{{Cos[t]*(Cos[t] - Sqrt[3 + Cos[t]^2]), (Cos[t] - Sqrt[3 +
Cos[t]^2])*Sin[t]},
  {Cos[t]*(Cos[t] + Sqrt[3 + Cos[t]^2]), (Cos[t] + Sqrt[3 +
Cos[t]^2])*Sin[t]}}

In[2]:=
ParametricPlot[Evaluate[xy], {t, 0, Pi}, AspectRatio -> Automatic]

works well.

Peter


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