The 400-word article on math diary Circle -20 1X year x month x day x week x sunny.
We have just learned about circles (1) and (2), and learned a lot about circles. From the understanding of circles, we understand the application of the circumference of circles, which can solve problems in real life. Let's learn about the circumference of a circle!
When I first started to learn the circumference, I learned that the circumference can be measured by rolling method and winding method, and I found that the circumference is always more than three times the diameter. In fact, the quotient of the circumference divided by the diameter of the circle is a fixed number. We call it pi. Do we use letters? The calculation is usually 3. 14. We get a formula: if the circumference is represented by c, then C=? D or C=2? R is circumference = pi? Diameter. The circumference has three applications: 1. It is known that d is C=? D 2。 If it is known that r first seeks c, d then seeks C 3. If c is known to find D = C, r is known to find d first and then r.
Given that d can be found, c: The diameter of the circle is 5.5 decimeters. What is the circumference of this circle? 3. 14? Diameter 5.5 = 17.27 decimeter.
Given R, we can find C: The radius of a car wheel is 0.3 meters. How many meters does it roll 1 time? How many meters 1000 laps do you roll? How many meters did it roll forward? Is to find the circumference of this wheel, first find the diameter: 0.3? 2=0.6m, and then find the circumference of a circle: 3. 14? 0.6 = 1.884m Finally, how many meters did 1000 lap advance: 1.884? 1000= 1884m .
It is known that C is D: the circumference of the flower bed is 62.8m Can you calculate the diameter of this round flower bed? Circumference 6.283. 14 = diameter 2m.
It is known that C can find R: the circumference of a circle is 25. 12㎝, and to find the radius of this circle, first find the diameter of this circle: use the circumference of 25. 123. 14=d 8㎝ and then find the radius: 8? 2=4㎝。
These are four typical examples of the circumference. The circumference of a circle divided by its diameter is a fixed number. what's up 3. 14.
There is another kind of topic: the picture below shows a semi-circular chicken farm with a fence on one side and a bamboo fence on the other. The diameter of this semicircle is 6 meters. How long is the fence? The problem is to find the circumference of a semi-circle. The side against the wall does not need to count the fence, that is, the half circumference of the circle is calculated, just use the diameter 6m3. 14= the circumference of the circle 18.84m and then calculate the half circumference: 18.84? 2 = 9.42 meters.
This is the circumference of an interesting circle, half a circle, which makes mathematics closely connected with life. It turns out that mathematics also contains the mystery of life!
Math diary's 400-word article 2 is circled 20 1X year x month x day x week x sunny.
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 it is very useful? Take it, some say that everyone is fighting for radius, and the class is very lively. 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 a rectangle.
Because: rectangular area = length? extensive
So: the area of the circle =C/2? r=2？ r/2？ r=？ r2
After the decomposition and reorganization of the graph, I know how to find the area of the circle! Math is amazing ~B
Math diary's 400-word article 3 circled 20 1X year x month x day x week x sunny.
I found a problem when I was doing my homework today. This is the cycle in life.
What is a circle in life, that is, what is the circumference, area and symmetry axis of a circle in life, that is, the application of circle knowledge in life.
In our real life, there are many places where circles are needed. As long as you observe carefully, you will find it. Although I don't know how much you know about circles, today I will tell you what I know. As far as I know, the distance traveled by the wheel is the circumference of this circle. The route that the minute hand of the clock passes is the circumference of the clock face; The length of the cloth edge around the round dining table is also the circumference of the table top; The bracelet that people often wear on their hands also contains too much knowledge about the circumference. I only said a little, and your master will observe the rest.
The circular area is actually very simple, as long as you can observe it and your eyes are brighter. The size of the round table is also the area of the round table; The size of the surface swept by the hour hand is also the area of this clock; There is also a possibility that everyone is rare, that is, tie the cows up with ropes to eat grass, and seek the maximum range of grazing for the cows, that is, the area of the circle. This is what I summed up.
Also, a circle has countless axes of symmetry, remember!
That's all I know, not much. The so-called: There are mountains outside the mountains, but there are people outside the people? Please advise.
In fact, there is a lot of mathematics in life, depending on your carefulness. Do you know that?/You know what?
After reading math diary's 400 words about the circle, I will still read:
1. Four math diary in my study circle.
2. math diary's 300 words about the circle
3. math diary is about 400 words.
4. Four 400-word compositions written by math diary in the fourth grade of primary school.
I'm exhausted. I tried several methods. I thought of this method at the beginning, but finally forgot to extend