1, you need to know the basic structure and scale of protractor. The protractor is a semi-circular tool marked with scales from 0 to 180 degrees. Each scale represents an angle, and the more the scale goes to the center, the greater the angle.

You need to determine the angle to be measured. Draw an angle on the paper or blackboard, or find an angle on the object you want to measure.

You need to put the protractor in the corner. Put the center of the protractor on the vertex of the angle. In this way, the semi-circular edge of the protractor coincides with one side of the corner.

4. You need to read the value of the angle. There are two scales on the protractor, which correspond to the inside and outside of the angle respectively. You can choose which scale to use according to your own needs. Find the tick mark that coincides with the angle, and then read the value on it.

5. Record the angle value you read. This value is the size of the angle you want to measure.

6. When measuring the angle with a protractor, make sure that the center point of the protractor coincides with the vertex of the angle. If they are not consistent, the measurement results may be inaccurate. In addition, you need to pay attention to choose the correct scale to read, otherwise it will also lead to measurement errors.

The purpose of measuring angle:

1. Understanding the shape and structure: By measuring the angle, we can understand the size and structural characteristics of the shape. For example, in mechanical design, the shape and size of parts are determined by measuring angles to ensure their smooth assembly.

2. Judging the angle: In some application scenarios, it is necessary to judge the angle. For example, when shooting, driving or operating mechanical equipment, it is necessary to accurately judge the direction and angle of the target to ensure accurate aiming or operation.

3. Calculate the sum or difference of angles: In some geometric problems, it is necessary to calculate the sum or difference of angles. By measuring the angle, we can determine the size of the angle and further calculate the relationship between them.

4. Establish an angle model: In geometry, physics or other disciplines, it is often necessary to establish an angle model to study the motion, balance or force of an object. By measuring angles, the size and relationship of each angle in the model can be determined.

5. Solve practical problems: In some practical problems, a quantitative perspective can help people better understand and solve related problems. For example, in architecture, the direction, height and appearance of buildings are determined by measuring angles; In the aerospace field, the safe flight of aircraft is ensured by measuring the angle.