Angle is a basic geometric concept in mathematics, which can be defined as a graph composed of two rays drawn from a point. This definition is usually abbreviated as "ray pattern". On a more specific level, an angle can be defined as the included angle between two adjacent projections of a ray with a common endpoint and another ray within a range of less than 360. This definition emphasizes the basic feature that an angle consists of two rays (or line segments) and their common endpoints.

The definition of angle includes two main parts: size and direction. Size refers to the angle included in an angle, usually expressed in degrees or radians. Direction refers to the direction pointed by the angle, that is, from which direction the light extends.

The basic concept of angle is based on Euclidean geometry, but it was later extended to non-Euclidean geometry. In non-Euclidean geometry, the definition of angle is no longer based on the concept of ray, but on the concept of curve. In this case, the angle is defined as the angle between a point on a curve and two adjacent tangents or the angle between two adjacent tangents.

In addition to its application in geometry, the concept of angle is also widely used in other fields of mathematics, such as algebra and trigonometry. For example, in trigonometric functions, the angle is used to describe the position of the angle relative to the reference axis, usually expressed in degrees or radians. In trigonometric functions, the angle usually ranges from 0 to 360 or from 0 to 2π radians.

In a word, angle is a basic geometric concept, which can be used to describe the included angle between a point and two adjacent rays. This concept is widely used not only in geometry, but also in other fields of mathematics.

In mathematics, angles can be divided into many types, including but not limited to the following:

1, acute angle: an angle greater than 0 and less than 90 is called an acute angle.

2. Right angle: An angle equal to 90 is called a right angle.

3. Oblique angle: An angle greater than 90 and less than180 is called obtuse angle.

4. Flat angle: The angle equal to 180 is called flat angle.

5. Fillet: An angle equal to 360 is called a fillet.

6. Negative angle: The angle formed by clockwise rotation is called negative angle.