1, origin:
Mathematically, the origin of the number axis is 0, and the origin of the coordinate system refers to the intersection of the coordinate axes. Together with the positive direction and unit length, it is called the three elements of the number axis, and all three are indispensable. In the two-dimensional rectangular coordinate system, the coordinate of the origin is (0,0). In the three-dimensional rectangular coordinate system, the coordinate of the origin is (0,0,0).
The origin plays the role of reference datum in the number axis, two-dimensional and three-dimensional coordinate systems, and the coordinates of other points can be calculated according to this point.
Step 2 be positive
The positive direction is the specified direction, and the opposite of the positive direction is the negative direction. On the number axis, it is one of the three elements; It is also an indispensable part of the coordinate system. The purpose of introducing the concept of "positive direction" is to better analyze and express problems.
3. Unit length
The length of the unit. The unit 1 is an artificial reference standard, and the unit length is a reference standard. It has no fixed value and varies according to the setting, so it is not an actual unit of length measurement.
The distance from the origin to the number 1 is not a specific length measurement standard.
Extended data
Number axis action
1, the number axis can visually represent numbers, and the points on the horizontal number axis correspond to real numbers one by one, that is, each real number can be represented by a point on the number axis.
2. Compare the sizes of real numbers, with 0 as the center, and the number on the right is greater than the number on the left.
3. The imaginary number can also be represented by the vertical number axis perpendicular to the horizontal number axis and with the same origin, thus forming a complex plane with the horizontal number axis.
4. Two mutually perpendicular number axes with the same origin can form a plane rectangular coordinate system; Three mutually perpendicular number axes with the same origin can form a spatial rectangular coordinate system to determine the position of an object.
The number axis has the completeness of numbers, which can represent both rational and irrational numbers (collectively called real numbers) and imaginary numbers. At the same time, a coordinate system can be established to form a relatively strict digital system.