3 line segments (AB, AC, BC)

6 lights (A to left, C to right, AC, BC, CB, BA)

As shown in the figure:

Judgment method:

1, a straight line consists of countless points. A straight line is a part of a surface and then constitutes a body. There is no end point, it extends infinitely to both ends, and the length cannot be measured. A straight line is an axisymmetric figure.

2. Connect two points with a ruler to get a line segment. The length of a line segment is the distance between these two points.

3. Ray refers to a straight line formed by the infinite extension of one end of a line segment. A ray has only one endpoint, so its length cannot be measured.

Various graphic representation methods of extended data

1. straight line: you can get a straight line by extending both ends of the line indefinitely, and the straight line has no end points.

One lowercase letter or two uppercase letters. But the word "straight line" must be added in front, such as: straight line L; Straight line m, straight line ab; Direct CD

2. Ray: One end of an infinitely extended line segment can get a ray, and the ray has an endpoint.

Lowercase letters or uppercase letters at the end, uppercase letters on the ray, and the word "ray" must be preceded, such as: ray a; Ray OA.

3. Line segment: You can get a line segment by connecting two points with a ruler; A line segment is a part of a straight line. A line segment has two endpoints, and its length is limited. The length of a line segment is the distance between two points.

Represented by capital letters representing endpoints, such as line segment AB; Represented by lowercase letters, such as line segment a.