A number pair consisting of two ordered numbers A and B is called an ordered number pair, and is denoted as (A, B).

2. Plane rectangular coordinate system

In a plane, two mutually perpendicular number axes with coincident origin form a plane rectangular coordinate system.

The horizontal axis is called X axis or horizontal axis, the vertical axis is called Y axis or vertical axis, the intersection of the two coordinate axes is the origin of the plane rectangular coordinate system, and the plane where the coordinate system is established is called the coordinate plane.

3. The law of coordinate symbols of points in each quadrant and coordinate axis.

First Quadrant (+,+) Second Quadrant (-,+) Third Quadrant (-,-) Fourth Quadrant (+,-)

(+,0) or (-,0) on the X axis, (0,+) or (0,-) on the Y axis.

4. Coordinates of special position points

(1) Coordinate characteristics of points on the bisector of two axes.

The horizontal and vertical coordinates of the points on the bisector of the first and third quadrants are equal.

The horizontal and vertical coordinates of the points on the bisector of the second and fourth quadrants are opposite to each other.

(2) Coordinate characteristics of points on straight lines parallel to the X axis and the Y axis.

5. Distance from point to X axis and Y axis

The distance from point P (a, b) to X axis is, and the distance from point P(a, b) to Y axis is.

6. the symmetry point of point P(x, y) about the x axis is (x, -y).

The symmetry point of point P(x, y) about the y axis is (-x, y).

The symmetrical point of point P(x, y) about the origin is (-x, -y).