Acute angle: An angle less than 90 degrees is called an acute angle. For example, the acute angle of a right triangle is 50 degrees. Right angle: An angle equal to 90 degrees is called a right angle. In geometry, right angle is a very important concept.

Obtuse angle: An angle greater than 90 degrees and less than 180 degrees is called obtuse angle. One obtuse angle is 120 degrees, and the other is 70 degrees. Flat angle: An angle equal to 180 degrees is called a flat angle. On a straight line, two rays extend from a point to form a right angle.

It may be difficult for sophomores to understand these concepts, but they can better understand the classification of angles through observation and practical operation. For example, we can let them draw various angles with their fingers, or make models of various angles with toy sticks and tape, which can help them better understand the classification and measurement of angles.

The names of each part of the angle include:

Vertex: the midpoint of an angle, that is, the intersection of two rays. Ray: Two rays from a vertex, which form an angle. Edge: The line segment between the endpoint and the vertex of the light, which is also the boundary of the angle. Angle can be further divided into acute angle, right angle, obtuse angle and other types. Wherein the acute angle is less than 90 degrees, the right angle is equal to 90 degrees, and the obtuse angle is greater than 90 degrees but less than 180 degrees.