This topic examines the understanding of lines, rays and line segments. In geometry, light is usually visually regarded as the light emitted by a flashlight.

Be familiar with the definition of ray, which refers to a straight line and a point on its side. In Euclidean geometry, a figure consisting of a point on a straight line and its edges is called a ray or a semi-straight line. Know that the light emitted by flashlight is called ray.

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 it is impossible to measure its length (it is infinitely long). In Euclidean geometry, the figure formed by a point on a straight line and its edge is called a ray, and this point is called the endpoint of the ray. For the light in geometry, we usually visually regard it as the light emitted by a flashlight.

The importance of learn mathematics:

1. Mathematics is closely related to our life. To say that the real effect of learning mathematics is not reflected in exam-oriented education, but in my own thinking about the future.

2. The importance of mathematics is self-evident. Mathematics is the foundation of all sciences and an important channel to cultivate logical thinking. It can be said that every major progress of our mankind is strongly supported by mathematics.

3. The application of mathematical knowledge in life is everywhere. From the calculation of daily living costs, to astronomy, geography, quality control, agricultural economy, aerospace, there are shadows of using mathematics.