1 and quadrant are four areas divided by horizontal axis and vertical axis in plane rectangular coordinate system (Cartesian coordinate system), and each area is called a quadrant.

2. It is mainly used in trigonometry and coordinate system in complex numbers. The quadrant takes the origin as the center and the X axis and Y axis as the dividing line.

3. The upper right is called the first quadrant, the upper left is called the second quadrant, the lower left is called the third quadrant, and the lower right is called the fourth quadrant. The points on the coordinate axis do not belong to any quadrant.