Different from the rectangular coordinate system in mathematics, its longitudinal axis is X axis and its horizontal axis is Y axis. On the projection plane, the rectangular coordinate system with the projection of the central meridian of the projection belt as the adjustment axis, the equatorial projection as the horizontal axis (Y axis) and their intersection as the origin is called the national coordinate system, otherwise it is called the independent coordinate system.
2. Mathematical plane rectangular coordinate system
Draw two orthogonal axes with a common origin on the plane, where the horizontal axis is the X axis and the vertical axis is the Y axis. In this way, we say that a plane rectangular coordinate system is established on the plane, which is called the coordinate plane, and the common origin of the two coordinate axes is called the origin of the rectangular coordinate system. The X axis and Y axis divide the coordinate plane into four quadrants, the upper right axis is called the first quadrant, and the other three parts are counterclockwise.
After establishing the plane rectangular coordinate system, we can determine its coordinates at any point on the coordinate system plane. Conversely, for any coordinate, we can determine a point it represents on the coordinate plane.
For any point C on the plane, the intersection point C is perpendicular to the X-axis and Y-axis respectively, and the corresponding points A and B perpendicular to the X-axis and Y-axis are respectively called the abscissa and ordinate of the point C, and the ordered number pairs (A, B) are called the coordinates of the point C. 。
In any two points, if the abscissas of the two points are the same, the connecting line of the two points is parallel to the longitudinal axis; If the vertical coordinates of two points are the same, the line connecting the two points is parallel to the horizontal axis. Geometry can be proved in this way.