# Circle as an implicit equation in polar form

- Author:
- Alexander Thaller

- Topic:
- Circle, Conic Sections

The general polar equation of a circle of radius centered at is
.
This equation is derived from the Law of Cosines.
Using that and we can transform this polar equation to a cartesian one:

Instead of the we use

*atan2(y,x)*in GeoGebra, as this function gives us an angle in [0,360)Another possibility is to use the general circle equation in cartesian form
and substitute and so we get
as the implicit equation.

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