Through observation, operation and other activities, we can understand the meaning of angle, know the protractor and use it correctly. The following is the measurement courseware of mathematical angle in the first volume of the fourth grade of People's Education Press, which I compiled for you. Welcome to reading.

Teaching requirements:

1. Make students know the protractor, know the scale structure of protractor, know the arrangement order of scales in different directions on protractor, know the measurement unit of angle "degree" and know the angle 1.

2. Make students master the method of measuring angles and learn to measure angles with a protractor.

Preparation of teaching AIDS: projector, angle made of red wood, protractor for teachers and students.

Teaching process:

First, review the old knowledge.

1. Exercise 22, question 5. Show it on the little blackboard. Name the students and count them.

2. Determine which of the following figures is an angle.

3. Direct contrast angle.

Draw two corners with different sizes on the blackboard. The first angle is slightly larger. Then make a corner with mahogany strips, which is equivalent to drawing the second corner.

Compare the angle made of wood strips with the first angle.

Question: Which angle is bigger? How does it compare? Can you tell me how big it is? (can't)

The angle made of wood strips is compared with the second angle.

Question: What are the sizes of these two angles? How does it compare? Can you tell me how big these two angles are? (can't)

If I can tell how big the angle of the mahogany strip is, can you tell how big the second angle is?

4. Introduce the topic.

We can directly compare the sizes of the two angles, but we can't tell how big they are. If you can measure the angle in units like a line segment and know the size of the angle, it is easy to know the size of the angle. So, what do you use to measure? What is the unit of measurement? How to measure the angle? These are what we will learn in this lesson-angle measurement. (blackboard writing topic)

Second, know the protractor

1. The unit of measurement of cognitive angle.

Note: To measure the angle, you need a protractor. This is a protractor. (Display protractor)

Let's meet the protractor first. (Projection protractor)

Question: What shape is the protractor?

Now let's look at this semicircle, starting from 0 and ending at 180. Think about it, how many parts is this semicircle divided equally?

Note: Divide the semicircle into 180 parts, and the angle of each part is called 1 degree angle. (Draw an angle of 1 degree by passing a line through the center of the protractor.) In other words, the unit for measuring the angle is "degree". (Blackboard: Degrees) Writing "Degrees" can be represented by a small circle, which is "1 Degrees". Let's write it like this. (blackboard writing:)

Lead the students to read "1".

Follow-up: What is the unit for measuring angles? What is the angle of 1'? (Observe again through the angle of drawing the wire)

It is pointed out that the unit of measuring angle is "degree", which is represented by the symbol "'".

2. Understand the structure of protractor.

(1) Divide the semicircle into 180 equal parts, each part is 1', and the corresponding angle of such 10 part is 10 degree. (Pull out 10 degree angle, and combine books: 10. So the right angle of 60 parts is 60 degrees. Pull out a 60-degree angle and write 60 on the board. These 90 copies are at a 90-degree angle. (Pull out a 90-degree angle and combine the book: 90)

(2) Please continue to observe. This point (center) on the protractor is called the center of the protractor. (Blackboard: center) Look carefully again. How many circles are there on the protractor? How are the scales of the outer ring 0 ~ 180' arranged? What about the inner ring?

It is pointed out that there are two scales on the protractor, the outer scale goes from 0 to 180 clockwise from left to right, and the inner scale goes from 0 to 180 counterclockwise from right to left. Students, do you understand?

(3) Now look at the scale line of the outer ring. Do you see the O tick mark on the left? Tie a knot at one end of the line and coincide with the center. Draw out 10, 30, 90, 120, 180 with lines, and ask the students to tell what the degree is.

Question: Who can find the scale line of the outer ring 50 from the left? Please pull this line to show it. (Name demonstration)

Who will find the graduation line of 90? (Name demonstration)

Please find out the scale line of outer ring 125. (name demonstration) 180?

Will the scale of the outer ring be discovered?

(4) Starting from the right, how to find the scale of the inner ring? Now who will pull the line to show the scale line of the inner ring 0? (Name demonstration) What about 45?

Which student came to find the 80 in the inner circle? (Name demonstration) What about 90?

Then ask the students to find out the tick marks of 140 and 180 by pulling the wires.

Have you found the scale of the inner ring?

Please take out your own protractor. Is it the same as the teacher's? Where is the center of your horn?

Let's look for the scale on the protractor. From the left, find the 0 scale mark, 10 scale mark, 135 scale mark and 180 scale mark. Starting from the right, find the tick marks of 0, 10, 135 and 180. (Teacher's inspection)

Third, the measurement method of teaching angle

1. Self-study textbook.

We know the protractor, which can indicate the degree on the protractor. How to measure the degree of an angle with a protractor? Please read the textbook. Start from the penultimate line on page 11and end with1. Tell the teacher after reading it, how many steps does it take to measure the angle? What are the steps?

2. Question: How many steps should the angle be measured? Which two steps?

It is pointed out that the method of angle measurement can be summarized as "two coincidences, one depends on the number"

The teacher used a small blackboard to show:

Coincidence: the center of the protractor coincides with the vertex of the angle, and the O scale coincides with one side of the angle.

Look at the number: Look at the number of scales on the other side of the corner.

Please measure this angle with the teacher. (Projecting an angle of 40) Put the protractor on the angle first, and then achieve "two coincidence". (demonstrate the method of coincidence while talking)

Look at the scale number of the other edge pair. Do you know what the angle is now? How do you know that? Why look at the inner ring?

Point out: Pay special attention when measuring the angle to find out which circle to look at. Here, the O scale line of the inner circle starting from the right coincides with one side of the corner. Find out how many degrees the other side is counterclockwise. This side is 40, and this angle is 40. You can write it like this. (blackboard writing: 40)

4. practice.

In this way, please measure the degrees of three angles in the "Practice" and write them down below the angles. When measuring, place the protractor according to the position of the protractor shown in the figure. (Teacher's patrol guide)

Question: How many degrees is each angle?

5. Question: Please have a look. Example 1 12 has two angles. Are they the same size?

Think about it, how can we know if they are the same size?

Now, please measure these two angles and compare their sizes.

Question: What is the angle on the left? (blackboard: 30) what about the right corner? (blackboard writing: 30)

Question: What are the sizes of these two angles? Why?

When comparing just now, we can see that these two angles are the same size. What's the difference when drawing? Does the angle have anything to do with this?

It is pointed out that there are two rays on both sides of an angle, which can extend indefinitely. Therefore, the size of the angle has nothing to do with the length of the drawn edge.

Follow-up: What does the angle have to do with it? Show it again from the angle of wooden strips, indicating that it has something to do with the size of forks on both sides. )

6. Compare the sizes of the two corners that appear at the beginning of the course.

Now let's measure the degrees of the two corners on the blackboard at the beginning of the class. (Teachers and students measure and record the degree together)

Can you tell me how big these two corners are now? How many degrees is the first angle larger than the second angle?

Fourth, class summary.

Through the study of this lesson, we can know exactly how big an angle is and how different it is. Now, who will tell us what we have learned in this class? What knowledge have you learned? How to measure the angle with a protractor?

Note: When measuring the angle with a protractor, you should also pay attention to which circle to look at.

Verb (abbreviation for verb) class assignment

1. Please measure the degrees of the three angles in Exercise 22, Question 6, and write them in the textbook.

2. Exercise 22, question 7.