1, the abscissa of the first quadrant is positive, and the ordinate is positive. In the plane rectangular coordinate system, the first quadrant is on the positive semi-axis of the X axis and the Y axis, and is the upper left corner of the four quadrants. In this quadrant, the abscissa and ordinate of points are positive numbers, for example, the vertices A, B, C and D of a square are all in the first quadrant.

2. The abscissa of the second quadrant is negative and the ordinate is positive. In the plane rectangular coordinate system, the second quadrant is on the negative half axis of X axis and the positive half axis of Y axis, and it is one of the upper left corners. In this quadrant, the abscissa of a point is negative and the ordinate is positive, such as the vertex e of a square in the second quadrant.

3. The abscissa of the third quadrant is negative and the ordinate is negative. In the plane rectangular coordinate system, the third quadrant is on the negative semi-axis of the X axis and the negative semi-axis of the Y axis, and it is one of the lower left corners. In this quadrant, the horizontal and vertical coordinates of points are negative, for example, the vertices f, g and h of a square are all in the third quadrant.

4. The abscissa of the fourth quadrant is positive and the ordinate is negative. In the plane rectangular coordinate system, the fourth quadrant is on the positive semi-axis of the X axis and the negative semi-axis of the Y axis, and there is one in the lower right corner. In this quadrant, the abscissa of a point is positive and the ordinate is negative, for example, the vertex I of a square is in the fourth quadrant.

Application of some mathematical quadrants;

1, trigonometry and coordinate system in complex numbers: Quadrants can be used to represent trigonometric functions and coordinate systems of complex numbers. For example, the function image of sin(x) is the curve between the first quadrant and the second quadrant.

2. Coordinate system on the map: On the map, the first quadrant can be used to represent east longitude and north latitude.

3. Income and expenditure relationship in economics: In economics, the first quadrant can be used to represent the relationship between income and expenditure, and the second quadrant can be used to represent the relationship between investment and income.

4. Relationship between force and acceleration in physics: In physics, the relationship between force and acceleration can be represented by the second quadrant, and the relationship between work and kinetic energy can be represented by the fourth quadrant.