Pole and polar line skillfully solve conic curve: polar line is usually a concept suitable for conic curve. If the tangent of a conic curve tangent to point A and point B intersects with point P, then point P is called the pole of straight line AB about the curve, and straight line AB is called the polar line of point P ... So the pole and polar line are interdependent.

In mathematics, polar coordinate system is a two-dimensional coordinate system. Any position in the coordinate system can be expressed by the included angle and the distance from the origin to the pole. Polar coordinate system has a wide range of applications, including mathematics, physics, engineering, navigation, aviation and robotics.

Polar coordinate system is especially useful when the relationship between two points can be easily expressed by included angle and distance. In the plane rectangular coordinate system, such a relationship can only be expressed by trigonometric functions. For many types of curves, polar coordinate equation is the simplest expression, and even for some curves, only polar coordinate equation can be expressed.