Solution: There are 1 lines in a straight line and no endpoints on the left and right, so there are 1 lines in a straight line and 8 rays, and there are 4 endpoints from left to right, that is, there are 8 rays;
Seen from the left, the first endpoint can form three line segments, the second endpoint can form two line segments, the third endpoint can form 1 line segments, and * * * has 3+2+ 1=6 line segments.
Important and difficult
This topic examines students' ability to analyze and answer questions according to the characteristics of line segments, straight lines and rays. According to the fact that a line segment has two endpoints, a straight line has no endpoint, and a ray has one endpoint to answer, it is the application of basic concepts, so you should be proficient.
Test site prompt
Analyze the meaning of the question and answer it according to the characteristics of line segment, straight line and ray;
Problem-solving skills
A line segment has two endpoints, a straight line has no endpoint and a ray has only one endpoint.
Combined with this question, we answer it according to the number of endpoints of line segments, straight lines and rays.
Expand knowledge:
A line is made up of countless points.
A straight line is a part of a surface and then constitutes a body. There is no end point, extending to both ends indefinitely, and the length cannot be measured. A straight line is an axisymmetric figure. It has countless axes of symmetry, one of which is itself, and all lines perpendicular to it (there are countless axes of symmetry). There is only one straight line between two non-overlapping points on the plane, that is, two non-overlapping points determine a straight line.
On the sphere, countless similar straight lines can be made after two points. The most basic element of geometry. In the axiomatic system of Euclidean geometry established by D Hilbert, points, lines and surfaces belong to basic concepts, which are defined by their relationships and five groups of axioms.
This concludes the introduction of the definition of straight line.
Definition of line segment:
A continuous or discontinuous figure composed of one or more different line elements, which is a limited part between two points on a straight line. The two endpoints of a line segment are represented by letters A, B or lowercase letters, which are marked as line segment AB or line segment BA, and line segment A .. where A and B represent the two endpoints of a line segment. Line segment is the concept of mathematics, which is a universal means for human beings to strictly describe abstract structures and patterns of things, and can be applied to any problems in the real world. All mathematical objects are artificially defined in essence.