Polar Coordinates of a Point
In a polar coordinate system, the coordinates of an ordered pair (r, θ) associated with the position of a point P, where r is the distance from the origin to point P and θ is the angle of rotation.
The origin O of the coordinate system is called the pole.
The distance r from the pole to point P is called the radius or polar axis.
The angle of rotation θ is called the polar angle or azimuth.