1, choose the right ruler: first of all, you need a soft ruler or metal ruler with accurate scale. Ensure that the ruler scale is clear and the error is small. Find the center of the circle: roll gently along the edge of the circle with a soft ruler or metal ruler, and observe the scale on the ruler at the same time. When the two ends of the ruler are aligned, this is the center of the circle.

2. Mark the center point: make a mark on the found center point, and you can draw a small mark on the circumference with a pen or blade. Measure the diameter: put one end of the ruler on the mark, and then pull the ruler vertically down to the edge of the circle. At this time, the scale on the ruler is the diameter of the circle.

3. Confirm the measurement results: Repeat the above steps for many times to ensure the accuracy of the measurement results. If the results of each measurement are similar, then it can be determined that this is the diameter of the circle. Recording results: record the measured diameter on paper or save it with electronic equipment.

The function of ruler

1, measuring length: The most basic use of a ruler is to measure the length of an object. Align the zero scale line of the ruler with the starting end of the object, and then read the corresponding scale at the end of the object to get the length of the object. Scribe: A ruler can be used to draw straight lines. On the paper or other surface, fix the ruler at one end, and then move the ruler to the other end to draw a straight line.

2. Angle measurement: Some rulers have angle scales, which can be used to measure angles. Align one end of the ruler with the starting point of the angle, and then rotate the ruler to the same angle as the target angle to get the angle. Calculate area and volume: Use rulers and scales to calculate the area and volume of objects.

3. Assisted learning: Rulers also have many uses in the field of education. For example, students can use rulers to draw charts, design models and conduct scientific experiments. Rulers can also help students understand geometric concepts, such as length, angle and area. Architecture and engineering: In the field of architecture and engineering, ruler is one of the necessary tools.