3
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I have defined the region as such:

Region[
 ParametricRegion[
  {r Cos[θ], r Sin[θ]},
  {{θ, 0, 2π}, {r, 0, 2+Cos[θ]}}
 ], Axes -> True,
 PlotRange -> All
]

However it only shows half of the limaçon:

enter image description here

Whereas the polar plot of the same function over the same interval [0,2π] represents the entire thing:

PolarPlot[2 + Cos[θ], {θ, 0, 2π}]

enter image description here

Now, I know I am using a workaround, by defining a polar plot with x and y, and this is likely the cause of the issue. So, how would I define the region that I want to, or any region really, using polar coordinates?

Note: Changing the interval to [-π,π] draws the full limaçon, but I would rather not have to play around with the interval every time I have a new function. I preferably want a solution that allows me to easily and correctly define a polar region.

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  • $\begingroup$ What is this Region function? It seems to be undefined in my version (v11.0)! $\endgroup$ – M. Stern Oct 21 '17 at 21:24
  • $\begingroup$ Are parametrized domains supported? $\endgroup$ – Kuba Oct 21 '17 at 21:34
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This works for me:

R = ImplicitRegion[(0 <= θ <= 2 π) && (0 <= r <= 2 + Cos[θ]), {r, θ}];
ParametricPlot[{r Cos[θ], r Sin[θ]}, {r, θ} ∈ R]
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