Plane polar coordinate system is a kind of coordinate system. Polar coordinate system A coordinate system consisting of poles, polar axes and polar diameters on a plane. Let a point o on the plane be called the pole, and a ray Ox from o be called the polar axis.

1, length unit: the unit length used to define the polar diameter.

2. Positive angle direction: usually the counterclockwise direction is positive.

3. Polar coordinate refers to a coordinate system consisting of poles, polar axes and polar diameters in a plane. The polar diameter of a pole is defined as zero, and the polar angle can take any value. Polar coordinates of points other than poles on the plane correspond to rectangular coordinates one by one. Polar coordinate system is widely used in navigation, engineering drawing and other fields.