Hello, everyone:

Today, I'm going to talk to you about the content of Unit 4 in Book 1 1 of the Nine-year Compulsory Education Six-year Primary School Mathematics People's Education Edition, and the understanding of the circle.

First, teaching material analysis

This course is the basic knowledge of geometry, which is not only an introductory course, but also the basis for studying "circumference", "area of circle", "cylinder" and "cone" in the future. Students often come into contact with circular objects in their daily lives, and they have initially understood the process in their lower grades, but they are all intuitive and superficial.

Second, said the teaching objectives

The new curriculum standard puts forward that mathematics teaching should be closely related to students' living environment, and based on students' experience and existing knowledge, we should create autonomous learning and cooperative communication learning methods, so that students can acquire basic teaching knowledge and skills through observation, operation and communication, further develop students' thinking ability, stimulate students' interest in learning and cultivate their self-confidence in learning mathematics well. Therefore, I set the teaching objectives of this class as the following three points:

1, knowledge goal: let students master the characteristics of circles and draw circles in various ways;

2. Ability goal: Experiential mathematics is closely related to daily life, which can explain the phenomena in life with the knowledge of circle or explain the characteristics of circle with the phenomena in life;

3. Emotional goals

In the activities of exploring new knowledge, cultivate aesthetic consciousness and stimulate students' feelings of learning and loving mathematics.

This kind of goal design breaks the law of traditional concept teaching, from paying too much attention to the concept itself to paying more attention to students' learning process and emotional experience, based on the diversification of teaching objectives.

4. Key points and difficulties

The teaching focus of this class is to further understand the characteristics of circles and their internal relations, so that students can deeply understand the close relationship with our lives. According to the characteristics of teaching materials and the actual situation of students in our class, I will determine the difficulty of this class as learning to draw a standard circle with compasses.

5, teaching AIDS and learning tools

Coursewares used in teaching include: geometric figures, pencils, rulers and compasses. These are the teaching AIDS and learning tools to be prepared for this class.

Third, talk about the methods of teaching and learning.

The new curriculum standard points out that teachers are organizers, guides and collaborators of learning. According to this concept, I follow the principles of stimulation, guidance, exploration and release. I carefully design activities to induce students to think, encourage students to communicate in general, and let students use their knowledge to make bold innovations. The status and degree of students' participation in learning activities as the main body is an important factor to determine the teaching effect. Therefore, the choice of learning methods embodies the idea of playing with middle school, playing with middle school, cooperating and communicating during learning and communicating and cooperating after learning. In order to show that students are the main body of learning activities, I designed the following teaching procedures according to students' learning situation:

Fourth, talk about the teaching process

(A), create a situation to stimulate interest

As soon as class began, I used the flag of the 2008 Olympic Games as a question, and my classmates immediately told me that it was composed of five circles. Then I will simply introduce the meaning of the national flag to the students to stimulate their patriotic enthusiasm, and then introduce the role of the circle in daily life as a topic to stimulate their desire for learning. At the same time, it also reveals the understanding of the theme circle.

(B), highlighting the main body and exploring new knowledge

1, initial perception circle

First of all, I will ask students to give examples from their lives. "Which objects are round in daily life?" Students may say: coins, CDs, road signs, clock faces, wheels, etc. These objects are all round. Let students initially perceive the circle and cultivate their spatial imagination.

Then, I will show two sets of numbers. The first group is rectangle, square, triangle, trapezoid and parallelogram, and the second group is the circle I just met. By comparison, it can be clearly seen that the first group of figures is surrounded by line segments connected end to end, while the circle is surrounded by curves, forming a correct representation-the circle is a curved figure on the plane.

2. Know the names and characteristics of each part of the circle.

(1) Find the center of the circle

In order to make students' learning process "action", through students' intuitive operation, students' various senses are mobilized to participate in learning, so that students can actively participate in the formation of knowledge. First, let the students fold the round paper prepared in advance and open it. Draw a crease with a pen and ruler, and repeat the origami activity on the round paper two or three times. After the operation, ask, "What did you find?" After the students did it themselves, they found that all the creases would intersect at one point. The intersection of these creases is right on the center of the circle. We call this point the center of the circle mathematically, and it is represented by the letter "O".

(2) Know the radius and diameter

In order to give full play to students' subjective role reasonably, and let students explore the formation and development of knowledge independently with their brains, hands, mouths and eyes, the line segment connecting the center of the circle with any point on the circle is called radius, and the radius is generally represented by the letter R, so that students can draw pictures by hand, measure and discuss in groups, and guide them to draw the conclusion that there can be countless radii in the same circle, and all radii are equal in length.

The line segment passing through the center of the circle with both ends on the circle is called the diameter, and the diameter is generally represented by the letter D. Because the knowledge of radius here is the foundation, I will try my best to let students discuss the knowledge of diameter in groups and guide them to conclude that countless diameters can be drawn on the same circle, and all diameters are equal in length.

(3) Discuss the relationship between radius and diameter.

What is the relationship between radius and diameter in a circle? Through measurement and comparison, let students understand and master the relationship between radius and diameter in the same circle, and let students use a formula with letters to express the relationship between radius and diameter. The letter formulas of d = 2r and r = d/2 are obtained.

3, master the method of drawing a circle

In the process of teaching circle drawing, I will also let students use their brains boldly and explore different methods of circle drawing. Students may think of drawing a circle with a round object, drawing a circle with a winding nail, drawing a circle with a compass and so on. Finally, I will try to make students draw a circle with compasses in the exercise book, and ask the steps to draw a circle while drawing. Through students' reports, I guided them to sum up the general steps of drawing a circle: (1) fixed point (the position of the center of the circle) (2) fixed length (the length of the fixed radius) (3) rotating to draw a circle. Then I will demonstrate the method of drawing a circle, emphasizing that the center, radius and diameter should be marked after drawing. Finally, I will emphasize that the center of the circle determines the position of the circle and the radius determines the size of the circle.

(3) Using features to solve problems.

Mathematics comes from life, and life is full of mathematics. The new curriculum standard points out that teachers should make full use of students' existing life experience and guide students to apply what they have learned in mathematics to reality, thus reflecting the use value of mathematics in real life. So in this session, I designed to let the students try to analyze why the wheels of our bicycles and cars are round with the knowledge of circles they have just learned, because the distance from the center of the circle to any point on the circle is equal everywhere, and the axes of the wheels are always on the same horizontal line when rolling, so they walk more stably and faster.

(4) Consolidate exercises

In order to help students consolidate their understanding of the meaning of radius and diameter, I designed such an exercise.

What is the radius in the 1. diagram? What is the diameter? Why not? Why not?

In order to help students consolidate their understanding of the relationship between radius and diameter, I designed a table.

2. Fill in the form:

R (m) 0.24 1.42 2.6

0.86 1.04

In order to further deepen the understanding of the circle and cultivate students' ability of analysis, reasoning and judgment.

3. True or false.

(1) The line segment with both ends on the circle is called the diameter. ( )

(2) All radii are equal. ( )

(3) A circle with a radius of 3 cm is larger than a circle with a diameter of 5 cm. ( )

(4) The center of the circle determines the position of the circle, and the radius determines the size of the circle. ( )

Finally, it fully embodies the application of circle knowledge in the field of mathematics and broadens our horizons. I designed an extended exercise:

Draw the largest circle in a rectangle with a length of 6 decimeters and a width of 4 decimeters. What is the radius of this circle?

In practice, I will conduct hierarchical training according to the differences of students' quality, so that students can master basic knowledge and improve students with learning ability, so as to achieve the goal of top-notch and "burden reduction".

Above, I only explained "what to teach" and "how to teach" from the aspects of teaching materials, learning situation, teaching methods, learning methods and teaching procedures, and made clear "why to teach like this". Talking about experience and lessons is still a new thing for all of us. I will talk about experience and lessons further in the future. I hope that experts and leaders will give valuable opinions on this lesson.