A lecture note on the preliminary understanding of right angles

As an excellent teacher, it is often necessary to write a lecture according to the teaching needs, which is helpful for students to understand and master systematic knowledge. How should I write the speech? The following is a sample essay of the lecture on "Preliminary Understanding of Right Angles" collected by me for your reference, hoping to help friends in need.

The teaching content of the lecture 1 on the Preliminary Understanding of Right Angles;

Textbook P40,41,examples 3,4 and corresponding exercises in Exercise 8.

Teaching objectives:

Combining life situations and operational activities, students can initially know right angles, judge right angles and draw right angles with triangles.

Teaching focus:

Students can initially know and judge right angles.

Teaching difficulties:

Can judge right angles, draw right angles with triangles.

Teaching process:

First, create situations and introduce new lessons.

(Show the activity angle) What kind of figure is this?

What does the angle matter?

The teacher demonstrated a right angle and asked, have you ever seen such an angle?

This angle is a right angle.

[Design Intention]: By reviewing old knowledge, stimulate students' interest in knowing right angles.

Second, cooperate in exploration and learn new knowledge.

1, teaching example 3.

(1) Where else have you seen this kind of horn? Tell the students in the group the angle you found.

Students communicate in groups and find out.

Discovery report.

(2) The teacher draws a right angle on the blackboard. Students observe the angle drawn by the teacher.

(3) Can you make a right angle? Think about what you are going to do, and then communicate in the group to know if you are doing it from the right angle.

Students think about how to make right angles and make right angles, and exchange ideas about right angles in groups.

(4) The teacher called the roll to report the method of making right angles. According to the student's report, decide whether to fold a piece of paper into a right angle: first, fold the paper in half, and then fold it into a right angle along the crease.

2. Teaching Example 4

(1) Is there any way to verify whether an angle is a right angle? Tell your method to the students in the group.

Discuss the method of verifying whether an angle is a right angle in groups.

(2) Student report verification method: Our triangle has a right angle. To know whether an angle is a right angle, you can compare it with the right angle on a triangle. Now please point out the right angle on the triangle.

Students observe the triangle and point out the right angle on the triangle.

(3) Please compare the right angles on the triangle to see which angles are right angles.

Students use right angles on triangles to compare which angles around them are right angles. Then report back.

Step 3 draw a right angle

(1) What else can right angles on triangles do?

Think back to how we drew an angle last class, and then please draw a right angle with the right angle on the triangle. After you finish drawing, tell the students in the group how you drew it.

Students recall the method of drawing corners, think about the method of drawing right angles, then draw right angles and exchange the methods of drawing right angles.

(2) Name the right angle of woodcut painting and talk about painting.

What should I pay attention to when drawing a right angle? Guide the students to summarize the drawing method of right angle.

[Design Intention]: By observing the objects in students' lives, make right angles, so that students can fully understand the characteristics of right angles and deepen their understanding of right angles. Ask students to judge right angles, draw right angles and other group activities. Students will know right angles better and judge right angles correctly. By reviewing the drawing method of angle, students are prompted to think about the drawing method of right angle and draw right angle correctly.

Third, the evaluation of learning effect.

1, complete the question 1 on page 4 1.

Can you find the right angle around us? Check it out and tell the students in the group.

Students are divided into groups to find the right angle and communicate.

2. Complete the second question on page 4 1.

Teachers guide students to complete independently.

Call the roll and ask how it was drawn.

Students draw right angles independently and think about how to draw. And report the painting method.

[Design Intention]: Through the practice of finding and drawing right angles in life, let students realize that right angles are around us.

Fourth, class summary.

What did we learn in this class?

The teacher instructed the students to organize their knowledge.

What did you get?

Postscript of teaching:

A right angle is a special angle. After learning the understanding of angle, students will have some knowledge after learning this part. In this lesson, let the students observe the real thing first, abstract the right angle from the real thing, and then let the students consolidate their understanding of the right angle through activities such as overlapping, drawing and comparing. It is difficult for students to draw right angles. Although the method can be learned, there are still some shortcomings in the actual operation process in some details. For example, when drawing another right-angled side, the drawn side is not straight because the ruler is not easy to press firmly; Another example is to draw a right-angled edge from the vertex, because the ruler is thick and thin, and the drawn edge cannot intersect with the edge. Let students practice painting more, and they will find skills when they are skilled.

Lecture Notes on "A Preliminary Understanding of Right Angles" 2 I. Teaching Ideas:

After the students have a preliminary understanding of the angle and know the shapes such as rectangle, square and circle, the teaching materials are arranged at right angles. There are two examples in the textbook, one is to abstract a right angle from the real thing, the other is to judge whether an angle is a right angle with the right angle on the triangle, and draw a right angle with the triangle. Especially when understanding the angle, the students first abstract the angle from the real thing, and there is a right angle, so I changed this mode in this class. After the students introduce the angle, they directly introduce the right angle, observe the figure of the right angle and know the symbol of the right angle.

Then find the right angle in life and put the three abstracted right angles in different positions, so that students can correctly perceive the right angle. Then, instruct students to use an irregular piece of paper to fold right angles, compare the size of the folded right angles with the right angles on the ruler, and draw a clear conclusion: all right angles are the same. Use the right angle on the triangle to judge whether other angles are right angles. Experience drawing, guessing and other operations and experience activities, so that students can gradually understand the right angle.

Teachers in the whole class create as many opportunities and conditions as possible for students' active learning, provide rich learning resources, and pay special attention to giving students enough time for independent exploration and operation experience as well as necessary guidance and help, which not only opens up the space for students to explore knowledge, but also changes students' learning methods, promotes students' active exploration, effective cooperation and full communication, and strives to turn the limited time and space in the classroom into an infinite space for everyone to participate and develop.

Second, the teaching objectives:

1, through activities such as finding, folding, comparing and drawing, let students know the right angle preliminarily; Learn to judge and draw right angles with right angles on triangles.

2. Experience a variety of operation experience activities to cultivate students' observation ability and hands-on operation ability.

3. Through discussion, exchange and evaluation, let students learn to cooperate with others, and communicate with others the process and results of thinking, so that students can initially form the consciousness of evaluation and reflection.

4. Understand the close relationship between mathematics and life. Experiential mathematics activities are full of exploration and creation, which stimulates students' interest in learning.

Third, the teaching focus:

When you know the right angle, you will judge the right angle and draw the right angle with the right angle on the triangle.

Four, teaching difficulties:

Will use the right angle on the triangle to judge the right angle and draw the right angle in different directions.

Five, teaching preparation:

A pair of triangular plates; A rectangular square paper and a round paper; Irregular paper and a few pieces of white paper.

Six, teaching link analysis:

Through the understanding and analysis of the teaching materials, I follow the following four steps to teach.

The first part is the introduction summary:

First, let the students introduce the "horn" and talk about the knowledge about the horn.

Then the right angle is introduced, and the relationship between angle and right angle is briefly summarized.

The second part is to explore knowledge:

The first level, the initial understanding of right angles. Firstly, the standard right-angle graph is given, which shows that right-angle is a special member of angle family. It has its own unique right-angle symbol, which looks like a "mouth" after marking-this solves the problem that the right-angle symbol made by students is not standardized. At the same time, as a member of the angle, it has the characteristics of the angle. After knowing the right angle, the communication activity I designed was "finding the right angle". Guiding students to find right angles in class can not only consolidate the judgment method of right angles, but also realize the wide application and aesthetic feeling of right angles in life and the application value of mathematics. Then through the different positions of the right angle, deepen the understanding of the right angle. Finally, through the activity of folding right angles, it is found that the sizes of these angles have not changed, and it is concluded that "all right angles have the same size" (judgment: 1, the size of right angles is related to the size of both sides, and the bigger the fork, the smaller the fork.

2. The right angle under the magnifying glass is the same as other angles, except that the side has become longer and the size has not changed. This is what they have in common. ) further form a right-angle representation to understand the concept more deeply.

By guiding students to observe, compare and give examples, teachers help students to discover and master new knowledge in independent inquiry activities, which is conducive to cultivating students' observation ability, developing students' practical ability, stimulating students' interest in learning, and enabling students to understand the close relationship between mathematics and human life.

The second level is to judge whether an angle is a right angle by the right angle in the triangle. In this activity, the teacher shows an angle close to a right angle, so that students can guess whether it is a right angle or not, causing cognitive contradictions, so that students can understand that the most scientific way to determine whether an angle is a right angle is to find a standard to measure it. At this time, let the students exchange the methods of judging right angles, and at the same time verify the scientific and reliable methods found. In this way, students have a strong curiosity and thirst for knowledge about new knowledge, so that students can actively participate in mathematics learning activities, which is conducive to students experiencing mathematics activities full of exploration and creation and stimulating students' interest in learning. There is a natural feeling. (But in this activity, the students' expression is not satisfactory. No students can sum up the method of judging whether an angle is a right angle by the right angle on a triangle, especially the students can't say the key word "coincidence". ) the third level, draw a right angle.

First, let the students try to draw a right angle with a triangle, and then introduce their own methods. Teachers organize students to study and discuss, give affirmation and guidance. Then the teacher will standardize the painting. Then assign exercises. Given a vertex and a right angle, how many right angles can you draw? How many can you draw for a side? How many angles can you draw if you only give a vertex? This design not only breaks through the teaching difficulty-drawing right angles in different directions, but also fully embodies students' subjective initiative, allowing students to experience the diversity of problem-solving strategies and develop the flexibility of students' thinking.

The third part is practical application.

First, cross the river at right angles.

Secondly, guess what kind of corner is hidden behind the picture. Further consolidate the method of judging the angle.

Third, develop students' comprehensive application ability of knowledge by calculating how many angles and several hidden right angles there are. The fourth part, through the introduction of right angle, combs the teaching knowledge plate of this course and forms the knowledge network.

Through the above four-step teaching activities, students can successfully complete the teaching tasks in the process of active observation, trial, verification, discussion and communication, and through the process of discovery, folding, comparison, drawing, thinking, speaking and practice, which embodies mathematics learning.

"Personal experience" enables students to gain an understanding of mathematics knowledge, and at the same time, they can make progress and development in thinking ability, emotional attitude and so on.

Seven, teaching design:

(1) Review and introduce:

1, introducing angle.

2, leads to a special angle-right angle.

(2) Operation query:

1, a preliminary understanding of right angles.

Summary: This name is well-achieved, and the word "straight" simply and vividly summarizes the characteristics of this angle. Briefly describe the relationship and difference between right angle and angle.

2. look for it.

(1) The teacher showed me a right angle and said, "Little friend, I am a right angle. I will celebrate my birthday in a few days. I want to invite my friends to attend. They look exactly like me. Can you find them in your life? " (In the form of stories, the right angle is presented to students in an anthropomorphic way, which not only avoids the single teaching of more abstract knowledge and the compulsory acceptance of difficult content, but also arouses students' infinite curiosity and competitiveness, so that students have a sense of relaxation in playing middle school. )

Students carefully observe and think, and find a corner in life. Students found that there was such an angle on the cover of the math book, on the desktop of the class and on the surface of the stool. There are such angles on the blackboard, switch, drawing window and glass in the classroom, as well as on the square table, coffee table, TV set and floor tile at home.

(2) Summary: Right angles are really "everywhere" in our lives! It seems to have a decisive role! We must remember it firmly.

3. Give me a discount.

(1) Children, are there right angles on these papers? There are right angles on rectangles and squares, but not on circular and irregular paper. Didn't the teacher just say that right angles are everywhere? Let's change it-fold it at right angles.

(2) Fold with completely irregular paper. Exchange questions: at least how many times? How do they fold separately? Can I fold it at will for the first time? Can I get a discount for the second time?

(3) Show an irregular piece of paper with straight edges, and ask: Guess how many times this paper can be folded at least to form a right angle? Verify again.

(4) Show the circle: How many times must it be folded at least to form a right angle? Why?

[health 1: I take a rectangular piece of paper, so when I fold it along a straight line, I get a right angle. He didn't completely fold in half, just aligned up and down, and the left and right sizes were different. )

Health 2: I take a square piece of paper, fold it in half first, and then fold it at right angles.

Health 3: I take a round piece of paper, and I can't make a right angle at a time, so I fold it in half along the line I just folded, then make a right angle, and then unfold it into four right angles.

Health 4: I have a simple method. Fold this corner of the square and there will be a right angle. Teacher: Children, carefully observe the angle of student 4. Do you have any different opinions?

Health 1: This angle is a right angle, and there is no different opinion.

Health 2: This angle is a right angle, but it is not folded, but on the original paper. ]

Students deepen their impression and memory of right angles through operating experience and perception of right angles, and form stereotyped right angles in their minds. Even if the folding method is different, the angle is the same. (Right angle) not only exercises students' operation ability, but also distracts students' thinking, and also paves the way for judging and drawing right angles. )

4. One ratio 1. Everyone has folded so many right angles. What is the size of the right angle? Is there any way to prove it? (overlapping method, comparison with right angles on triangles, etc. ). Summary: All right angles are the same size.

5. One to two. Compare right angles on triangles. Which angles are right angles? (scientific tools)

Show an angle close to a right angle, causing cognitive conflicts.

6. Draw a picture. The right angle said, "Little friend, can you draw a picture for me?" Draw a right angle with a triangle.

(1) Name a lifetime performance to try painting. Teachers and students * * * comment together and summarize the painting method.

(2) Exercise: How many right angles can a vertex and an edge draw? (2) Given only one vertex, how many right angles can you draw? (Countless) (Draw in the classroom exercise book) Solve the teaching difficulties and draw right angles in different directions.

(3) Practice improvement:

1, cross the river at right angles.

2. Guess. Guess what corner is hidden behind the picture? Further consolidate the method of judging the angle.

3. Count. Count how many angles and several hidden right angles there are to guide orderly counting and cultivate students' comprehensive application ability of knowledge.

The design of the above three exercises is from easy to difficult and puts forward different requirements. The purpose is to let students at different levels have the opportunity to show themselves, so that students at C and B levels can enjoy the joy of success, and at the same time satisfy the desire of students at A level to have enough to eat, and stimulate students' higher and longer learning enthusiasm. )

(4) Review and arrangement:

By introducing right angle, the teaching knowledge section of this course is sorted out and a knowledge network is formed.

Eight, teaching reflection:

Give and you will get. After careful reflection, I think the following points in this class are handled properly:

1, the combination of purpose and situation:

In teaching, a lot of content is abstract, which is difficult for teachers and students to learn. Students only learn abstract content by rote, not by understanding and memorizing. Right angles are abstract in the content of this book. In teaching, I changed the teaching method that the teacher told the students to listen. I skillfully personified a right angle into a living figure and showed it to the students in the form of stories, such as: "Can you find me in life?" "Can you draw a picture for me?" And other challenging languages have aroused students' strong interest and competitiveness, and they have learned new knowledge in relaxed play.

2. Give consideration to the learning needs of students at all levels, and embody hierarchical teaching.

Students are the masters of learning. If the students are not interested in mathematics, it will be useless for the teacher to work hard. In our usual teaching, it is found that the main reason why students are not interested in mathematics is that the teaching content is not suitable for students' actual level, especially those with learning difficulties. If they don't master the old knowledge, they will learn new knowledge, and the accumulation of mistakes for a long time can only be more boring. The implementation of hierarchical teaching in this course is reflected in the stratification of content and practice, so that students can fully mobilize their original knowledge and experience according to their respective learning levels and use their own way of thinking to solve different problems, so that each student can learn at a level suitable for him, get different degrees of development, have a sense of accomplishment, improve their interest in learning mathematics, and develop their initiative, enthusiasm and independence.

3. Improve teaching methods and set up scaffolding for students' thinking activities in time.

The new teaching view holds that mathematics teaching is the teaching of mathematics activities, and the process of mathematics learning is not a simple knowledge acceptance, but a student-centered mathematics activity. In the past, teaching was based on teaching, teaching before learning, and unconditional learning obedience and teaching, which made teaching become a single entity from * * *. In the teaching of this class, I try to change the original simple learning style, and provide students with objects to explore by creating scenarios, so that students can explore independently and actively participate in learning activities, so as to discover and master knowledge. In the process of cooperation and communication, students can not only show their ideas, but also inspire, absorb and supplement each other, so that their understanding can be gradually improved and deepened, and students can gradually form a personalized learning style.