The meaning of:

Is the unit for measuring angles, and the symbol is 0. A fillet is divided into 360 equal parts, and each part is defined as 1 degree (1 degree).

Basic introduction:

Use the number 360, because it is easily divisible. 360 has 22 real factors besides 1 and itself, including 2 to 10 except 7, so many special angles are integers.

In practical application, the angle of an integer is accurate enough. Sometimes more accurate measurements are needed, such as astronomy or the latitude and longitude of the earth. In addition to expressing degrees in decimals, degrees can be subdivided into minutes and seconds: 1 degree is 60 minutes (60') and 1 degree is 60 seconds (60 "). For example, 40.1875 = 4011'15 ". To be more accurate, seconds are expressed in decimals instead of adding units.

In mathematics, radian is used instead of angle, because the divisibility of 360 is not important to mathematics, and radian is more convenient in mathematics. The relationship between angle and radian is: 1 ≈ 0.0 174533 radian, 1 radian ≈ 57.29578.

The basic concept and classification of angle;

The basic concept of angle:

Understanding angle from a static point of view: the figure composed of two rays starting from a point is called angle.

Understand the angle from a dynamic point of view: a ray rotates around its vertex to another position, then the image formed by these two rays is called angle. A figure composed of two rays with a common endpoint is called an angle, the common endpoint is called the vertex of the angle, and the two rays are called the edges of the angle.

1, because the light extends infinitely to one side, the length of both sides of the angle is not important, that is, the size of the angle has nothing to do with its side length.

2. The angle can be measured and compared.

3. According to the degree of the angle, the angle can be divided into acute angle, right angle, obtuse angle, right angle and rounded angle.

Angle classification:

According to the degree of the angle, the angle can be divided into acute angle, right angle, obtuse angle, right angle and rounded angle.

1, right angle: 90 Angle, that is, the angle formed by the rotation of line OA around point O when the end edge is perpendicular to the start edge, is called right angle.

2. Acute angle: greater than 0. Less than 90. An angle smaller than a right angle is called an acute angle.

3. Oblique angle: greater than 90 degrees. Less than 180. An angle greater than a right angle and less than a right angle is called an obtuse angle.

4. Fillet: 360. The angle of, that is, when the ending edge coincides with the starting edge, the angle formed by the rotation of the light OA around the O point.

5. Boxer: 180. Angle, when the two sides of the angle are in a straight line, this angle is called a right angle. That is, the angle formed when the light OA rotates around the point O, and the end edge is on the reverse extension line of the starting edge OA.