First, teaching records

Teaching content: PEP compulsory education curriculum standard experimental textbook, the first volume of second grade mathematics.

Teaching material analysis: Symmetry is a basic graphic transformation. There are many symmetrical things in nature and daily life, and students are no strangers to symmetry. This lesson is carried out step by step in the order of knowledge introduction-concept teaching-knowledge application, which embodies the formation process of knowledge. I first designed the activity of "sticking dragonflies" to stimulate students' curiosity, and then guided students to observe a group of symmetrical physical pictures (leaves, pine trees, butterflies, fish, etc. ), analyzed their similarities and differences, and introduced the concept of "symmetry". Then I provided a paper-cutting activity for the students, who discovered the "symmetry secret" in the process of observation, communication and cooperation.

Teaching objectives:

1. Through the process of intuitive demonstration and hands-on operation, we can understand the symmetrical phenomenon and recognize the symmetrical figure.

2. Develop students' concept of space, and cultivate students' observation ability and hands-on operation ability.

3. Feel the close relationship between mathematics and life, and learn to appreciate the beauty of mathematics by appreciating biology and corresponding graphics.

Preparation of materials for learning and teaching: CAI courseware, scissors, colored paper and pictures.

Teaching process:

(1) Symmetry of situational activity and perception

1. Stick a dragonfly and feel "symmetry"

Teacher: (Playing by computer) Let's enjoy a beautiful picture together.

"Xiao He just showed his sharp corner, and the dragonfly had already stood on his head." On summer nights, we can often see dragonflies flying all over the sky. Today, the teacher also brought you two pictures of dragonflies. Who will mail them for me? Show pictures of red dragonflies and yellow dragonflies.

Teacher: Please observe the dragonflies posted by these two students and tell me what you find.

Health 1: The yellow dragonfly has the same wings on both sides.

Health 2: Red dragonflies have different wings. How can they fly? (All four wings are different in size)

Teacher: You speak very well! How can I make the red dragonfly fly!

Health 3: Just change its wings to the same size.

Teacher: Yes! In order for the red dragonfly to fly, it must have the same wings on both sides. (Pointing) Today, the teacher also brought you some pictures. (Paste half first, then paste the other half)

(There are: leaves, butterflies, clothes, gourds, trees)

2. Observe, discuss and reveal the theme

Teacher: Who can tell me what you found?

Health 1: I found that the teacher posted half and half.

Health 2: I found that the left half is as big as the right half.

Health 3: I found that these circles are the same size on both sides.

Teacher: Everyone speaks very well! Figures as big as two sides like this, we say they are symmetrical. Today, we will learn symmetry [blackboard writing].

[Comment: The introduction of interesting sticky dragonfly competition allows students to experience the process from special to general, and then to special, which is very clever, captures students' psychology, and allows students to experience and perceive symmetry in the activities of the game. From the perspective of participation, the whole class is highly motivated to mobilize and participate, and teachers attach great importance to the development of students' thinking, which naturally leads to topics through students' doubts. ]

(2) Hands-on operation and exploring symmetry

1. We'll discuss it after cutting.

Teacher: Can you try to cut such a symmetrical figure with scissors? Give it a try!

(teacher patrol, coach and map)

Teacher: Please stop your scissors first and let us enjoy these pictures together. () Which figures do you think are symmetrical? What are the asymmetries?

1: I think the graph 1, 2,3 is asymmetric.

Health 2: I also think Figure 4 is asymmetrical.

S3: I think the numbers 5, 6, 7 and 8 are symmetrical.

Teacher: (Refer to Figure 2) Can you tell me how it was cut?

Health: This is how I bend it with scissors.

Teacher: (Refer to Figure 3) Can you tell us how to cut it?

Health: I take the paper, cut it like this, and then cut it.

Teacher: Oh! So you can cut it at will. It seems difficult to cut out symmetrical figures.

Teacher: Let this classmate (Figure 5) show you how to cut it!

Health: I'll fold it like this first, and then cut it with scissors.

Teacher: Good! Come on, show it to everyone once.

(Refer to Figure 6) Can you introduce it to us?

Health: I'll fold it in half first, then cut it, and then I'll cut out this picture.

Teacher: Great! Think about it, class. Why can they cut symmetrical figures (No.5-8) and they can't (No.65438+No.0-4)? Where's the secret?

Victory seven said: they didn't fold in half.

Teacher: Please look carefully. What can you find in these symmetrical figures?

Health 1: sealed.

Health 2: There is a line.

Health 3: There are creases.

Teacher: Yes! Mathematically, this crease is called "symmetry axis". Please read it twice.

Teacher: Who can draw the symmetry axis of other figures? The rest of the students, please draw the symmetry axis in the figure you cut.

[Comment: Let the students cut the discussion and explore the secret of symmetry. Proper evaluation can arouse students' enthusiasm, expand their thinking space, pay attention to their emotional experience and highlight their dominant position. ]

2. Guess, discount.

Teacher: (showing a rectangular piece of paper) Is it symmetrical? Guess, how many symmetry axes does it have?

Teacher: How many axes of symmetry are there? Please start with 10% discount. Who can show it to you?

Teacher: Yes! A rectangle has two axes of symmetry. Guess again, how many symmetry axes does a square have?

Teacher: Who can tell how many symmetry axes there are in a circle? Then start folding.

Health 1: There is one.

Health 2: There are four.

Health 3: There are ten.

Health 4: There are one hundred.

Teacher: It seems that the students have different opinions, so we ask the computer for help. There are many symmetry axes on the computer screen, accompanied by a voice: I'm tired of folding, too, and I don't want to fold any more. )

Teacher: How many symmetry axes does a circle have?

Health 1: countless.

Student 2: Countless articles.

Teacher: Yes! A circle has countless axes of symmetry.

[Comment: It is difficult to tell how many symmetry axes a rectangle, a square and a circle have. Let the students guess, give a discount, give full play to the students' potential and subjective initiative, skillfully and effectively break through the difficulties and deepen the experience and understanding of symmetry knowledge. ]

(3) Expand the application and strengthen the appearance.

Teacher: In our daily life, besides these figures, many objects are also symmetrical. Can you give an example?

Examples of students are: desks, chairs, pencil boxes, erasers, windows, blackboards, clothes, planes, faces, people, etc.

Teacher: Can you point out where a person's symmetry axis is?

Teacher: Who can point out where the symmetry axis of the book is?

Teacher: In nature, many objects are symmetrical. Let's enjoy them together.

Computer play: butterflies, dragonflies, faces, deer, flying cranes, 8. Beijing Gymnasium, Eiffel Tower, folk paper-cutting, etc. )

Teacher: After enjoying the beautiful picture, do you want to cut it? Use your imagination and creativity to cut out more beautiful patterns! Give it a try.

(Play music when students start cutting)

Students cut out their works and paste them on the blackboard. )

Teacher: Who can tell us what you cut like?

Health 1: I cut it like a curtain.

Health 2: I cut it like a plum blossom.

Health 3: I cut like a rocket.

Health 4: I cut like a spaceship. I want to be an astronaut when I grow up.

……

[Comment: Let students realize that mathematics knowledge is around us, and mathematics is widely used in our lives. Teachers skillfully apply mathematics knowledge to science, art, architecture and other disciplines, paying attention to the integration of subject knowledge, which not only reduces the difficulty of students' understanding, but also makes monotonous content rich and colorful, further making students feel the fun and application value of mathematics learning. ]

(4) class summary

Teacher: Today we learned "symmetry". What impression did these symmetrical figures leave on you?

Health 1: Very beautiful!

Health 2: Very nice!

S3: Very interesting!

Teacher: Yes! These symmetrical figures are beautiful, and the teacher gave everyone a word "beauty". (paste a symmetrical "beauty")

[General Comment: This class adopts open classroom teaching, and students' enthusiasm has been fully mobilized. In teaching, teachers have fully created learning opportunities for students to practice, explore independently and cooperate with each other. In classroom teaching, students can actively learn knowledge, form skills and master mathematical methods through the process of attaching symmetry perception, cutting symmetry exploration, expanding symmetry and applying symmetry. ]

Second, after-class reflection

Mathematics curriculum standards point out that students' mathematics learning should be realistic, meaningful and challenging, and these contents should be conducive to students' active observation, experiment, guessing, verification, reasoning and communication. Effective mathematics learning activities cannot rely solely on imitation and memory. Hands-on practice, independent exploration and cooperative communication are important ways for students to learn mathematics. Combining the spirit of the new curriculum standard and reviewing the teaching of this class, I think the following three aspects are more prominent:

1. Make full use of students' life experience and let students learn actively in vivid and concrete situations.

Many objects (including buildings) in life are symmetrical, and it is easy for students to find their growing points by learning this knowledge. Therefore, in designing this class, whether from importing to exploring new knowledge or appreciating operation activities, I pay attention to making full use of students' life experience, so that all students can participate in practical activities with their hands, brains and mouths, and create a teaching situation close to students' lives.

Teaching is introduced by "Sticking Dragonflies" competition. I showed two dragonflies of different colors, red and yellow, so that the students could stick together in the competition. This design is because students are familiar with dragonflies. In the process of posting, students found that red dragonflies have different wings, so they smiled and said, "How can red dragonflies fly?" This also implies that dragonfly wings are the same size. The activity of sticking dragonflies has greatly stimulated students' curiosity and thirst for knowledge.

In the process of exploring "symmetry", I instructed students to cut paper and origami, and everyone experienced the process of cutting, and found that symmetrical figures could only be cut after being folded in half; The process of origami not only deepens students' understanding of symmetry axis, but also cultivates students' extreme thoughts.

2. Follow students' cognitive rules and further process teaching materials/articles/.

In the process of studying teaching materials, I found that the teaching materials developed gradually in the order of knowledge introduction-concept teaching-knowledge application. In the process of introducing knowledge, I used the way of "posting" to arouse students' questions: Why can't the red dragonfly fly? Can the yellow dragonfly fly?

When teaching "symmetry", I don't directly teach students to fold in half before cutting, but let students cut at will on the basis of finding that "both sides are the same size". In this way, some students who can cut will fold in half, and those who can't cut will understand from their demonstrations and introductions that "they must fold in half", and it is very easy to find the secret of symmetry.

3. Guide students to experience and construct their own mathematical knowledge in the process of hands-on operation and independent exploration.

In the process of exploring "symmetry" knowledge, let students try to cut it first, then compare and demonstrate it to reveal the secret of "symmetry", and then let students fully experience and appreciate "two sides are equal in size" through activities such as drawing a picture, guessing, overlapping and giving an example.

Consolidating application is the re-creation of students' learning knowledge. Students cite many examples of symmetrical objects around them and point out their symmetry axes, feeling that mathematics is in our life.

Finally, paper-cutting is the improvement of students' understanding and skills. The graphics they cut this time are very similar to the models of some objects in life. What's more worth mentioning is that some students fold in half first, then draw pictures and cut them. These cut figures really left a good impression on everyone, and the whole class ended with the word "beauty".

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