# polar coordinates

Polar coordinates are a coordinate system in which distances are measured from a fixed reference
point (the pole), and angles from a fixed reference line. There are two polar coordinations, *r* and *θ*, of a point *P* in the plane, where *r* is the point's distance from the origin and *θ* is an angle measured anticlockwise from some reference line emanating from the origin. **Spherical polar coordinates** incorporate a second angle, *φ*, which represents the angle of inclination of a line drawn to the point from a plane surface.

A **polar
equation** is one that uses polar coordinates.