Circle equation in polar system
The general equation for a circle with a center not necessary at the pole, gives the length of the radius of the circle.
The polar coordinate system is a two-dimensional coordinate system in which each point on a plane is determined by a distance from a fixed point and an angle from a fixed direction.
The fixed point (analogous to the origin of a Cartesian system) is called the pole, and the ray from the pole in the fixed direction is the polar axis. The distance from the pole is called the radial coordinate or radius, and the angle is the angular coordinate, polar angle, or azimuth.
|a||Radius of the circle (dimensionless)|
|r||Radius ( radial coordinate) (dimensionless)|
|r0||X-coordinate of the center of the circle (polar system) (dimensionless)|
|ϕ||Angle (angular coordinate) (dimensionless)|
|γ||Y-coordinate of the circle (polar system) (dimensionless)|