Polar Coordinate System

Overview

The polar coordinate system in a plane uniquely specifies coordinates using a pair of real numbers. At the center lies a point called the pole $O$. From the pole, a horizontal ray directed rightward is drawn. This is called the polar axis.

Let $⟨r,\theta ⟩$ be the coordinates of a point $P$. The first number $r$ is called the radial distance. It is the directed distance from the pole to $P$. The second number $\theta$ is called the polar angle. It is the measure of the angle from the polar axis to the line segment $\overline{OP}$.