The derivation method of pi is necessary as a prelude. Before introducing the derivation direction of circular area, we can review the derivation method of circular perimeter. In distant ancient times, Zu Chongzhi found that the quotient of the circumference and diameter of a circle was always fixed in the same number, and this number was an infinite acyclic decimal, that is? . In primary school, this number was taken as 3. 14. So, with the circumference C=2? R, which means C=? d .
The derivation of the product should not be too interesting at all.
Understand? After past lives, let's cut to the chase and tell you about the derivation process of circular area.
1, we can use the center and radius to cut the circle into several pieces. Put these small departments together. At first, it was not in the state.
2. Then, cut the fan frequently. At this time, the stitching began, and slowly, it became closer and closer to the ordinary parallelogram. Later, as the sector became smaller and smaller, the mosaic pattern was infinitely similar to a rectangle. Here, it is our key step.
Through simple observation and reasoning, we can easily find that the length of this magic rectangle is half of the circumference of a circle, and the width is the radius of a circle.
4, then you can get the area of this rectangle, that is, the area of the circle is C/2? R, the formula brought into the circle: S=? d/2？ r=？ r？ r=？ R2. How about it? Is it easier than expected?
Mathematics is a simple and complicated science. It's not a layman's humble opinion that the author said this, because my grade in primary school was the first at that time, so it was every year. You need to listen carefully to the study of primary school mathematics, and don't get in the way. About knowledge, be clear, clear every day, clear every week, and even clear every month. This method is suitable for learning behavior at any age and is still worth remembering.