The teacher asked us to fold the circle in the study tool and see what we can find from it. I wonder in my heart: a circle is a circle. What is there to fold? So let's fold the circle and understand the symmetry of the circle!

We took out scissors and cut a circle, and then cut it into eight parts on average. The teacher asked us to think about how to make the ball out of a circle. Some students say multiply by π, others say calculate by radius ... Everyone is full of arguments and the class is very active. Finally, the teacher asked us to try to put eight pieces of fan-shaped paper together. I spelled a figure similar to a parallelogram.

Then, we divide the circle into 16 and 32 respectively, and then put the cut small sectors together to form a polygon. At this time, I found that the more the average score, the closer the graph is to the rectangle.

Because: the area of a rectangle = length x width.

So: the area of the circle =C/2×r=2πr/2×r=πr2.

After the decomposition and reorganization of the graph, I know how to find the area of the circle! Math is amazing ~