Angle symbol:
There are two definitions of angle: static and dynamic:
① Static definition of angle: A graph composed of two non-overlapping rays with a common endpoint is called an angle. This common endpoint is called the vertex of the angle, and these two rays are called the two sides of the angle. ② Dynamic definition of angle: The graph formed by light rotating from one position to another around its endpoint is called angle. The endpoint of the rotated ray is called the vertex of the angle, the ray at the starting position is called the starting edge of the angle, and the ray at the ending position is called the ending edge of the angle.
The center of the protractor is aligned with the vertex of the angle to measure the angle. The zero scale line of the protractor is aligned with one side of the angle, and the scale pointed by the other side of the angle is the size of the angle.
Type of horn
The size of the angle has nothing to do with the length of the side; The size of an angle depends on the degree to which both sides of the angle are open. The bigger the opening, the bigger the angle. Conversely, the smaller the opening, the smaller the angle. In dynamic definition, it depends on the direction and angle of rotation. Angles can be divided into acute angle, right angle, obtuse angle, right angle, rounded corner, negative angle, positive angle, upper angle, lower angle and 0 angle, which are 10 respectively. An angle measuring system in degrees, minutes and seconds is called an angle system. In addition, there are secret system, arc system and so on.
Acute angle: An angle greater than 0 and less than 90 is called an acute angle. Right angle: An angle equal to 90 is called a right angle. Oblique angle: an angle greater than 90 and less than180 is called obtuse angle. Flat angle: The angle equal to 180 is called flat angle. Descriptive buckling angle of each angle: greater than 180 and less than 360 are called buckling angles. Lower angle: more than 0 and less than 180 is called lower angle, and acute angle, right angle and obtuse angle are all lower angles. Fillet: An angle equal to 360 is called a fillet. Negative angle: the angle formed by clockwise rotation is called negative angle. Positive angle: the angle of counterclockwise rotation is positive angle. Zero degree angle: an angle equal to 0 degrees.