Content: textbook of the first volume (the fifth volume) of the third grade of Beijing Normal University.

Course objectives:

(1) Knowledge and skills:

1, combined with specific things and graphics, through observation, operation and other activities to understand the perimeter.

2, can measure and calculate the perimeter of triangle, parallelogram, trapezoid and other graphics.

3, can be combined with specific situations, and perceive the close connection between the surrounding and real life.

(2) Process and method:

Let students deepen their understanding of circumference through practical activities such as drawing, touching, measuring and calculating.

(3) Emotional attitudes and values:

Through teaching, let students realize that there is mathematics everywhere in their lives and stimulate their awareness of learning and applying mathematics.

Teaching emphases and difficulties:

According to the requirements of curriculum standards and students' reality, I set "knowing and understanding the perimeter" as the teaching focus of this class.

"Calculation of the perimeter of triangle, trapezoid, etc." is established as the teaching difficulty of this course.

First, create situations and introduce new lessons.

Teacher: Students, do you know what season it is? Autumn is the season when leaves fall. The teacher collected pictures of all kinds of leaves from the internet. Let's enjoy them together. Please watch (play the courseware)

Second, independent exploration, cooperation and exchanges

Describe and say.

Teacher: Students, we enjoyed the leaves. Are they beautiful? Would you like to describe their shapes? The teacher gave you these beautiful leaf patterns. Please open the envelope, choose a favorite leaf pattern and draw its outline along the edge of the leaf with a colored pen.

Teacher: OK! Who wants to show you how to draw? (Physical projection display)

Please point with a pen and make it clear where to start and where to end.

The teacher concluded: It seems that no matter where we start, everyone draws a circle along the edge of the leaves. Please see (dynamic demonstration), the length of this week, we call it the perimeter of the leaves. (blackboard title: the length of a week)

Teacher: Teacher, there is still a small question: Who can tell you exactly where the starting point and ending point of your leaf pattern are? What did you find? The starting point and the ending point coincide. The figure formed by the coincidence of two points is a closed figure. (Blackboard: Closed Figure) Courseware: The length of a closed figure is called its perimeter.

Teacher: Let's look at the boundaries of a group of objects. If it is the perimeter of a closed figure, please sit down. Raise your hand if it is not the perimeter of the closed shape. If no one raises their hands, please explain the reasons for those who raise their hands and those who don't. )

Teacher: Well, the students did a good job. Now, please find a piece of paper with three numbers in the envelope and draw the edges of the numbers with strokes. Check each other between the same seats.

(2) find and touch.

1, the students drew really well and checked carefully! Now the teacher has some plane figures posted on the blackboard. Please choose a figure you like and draw its perimeter. And tell me what its circumference is. The length of a square is its circumference. )

2. The students did well. Can you find one side of an object in your life and talk about its circumference? (desk circumference, math book cover, blackboard, sole circumference, ...)

The teacher summed up: "The length of a figure in one week is the circumference", "The length of an object in one week is also the circumference",

(3) measure a quantity

Just now we know the circumference of a closed figure by touching, drawing and saying. Now the teacher will see if the students can calculate the circumference of the graph (show the courseware).

1. There are three numbers in the envelope. Please measure the perimeter of these figures and tell me the method you use. How to find the perimeter of a figure? Pay attention to starting from the "0" scale.

Note: The total length of the sides of these figures is the perimeter of these figures. Explain the process and results.

(Courseware shows answers)

2. Teacher: Through the previous study, the teacher found that the students in our class are good at observing and thinking, so the teacher still has a small problem. I hope the child can help the teacher solve it. Do you want it?

Third, consolidate practice and expand sublimation.

1. Teacher: The teacher wants to add a frame to this square photo. Where should I add the frame?

According to the students' answers, demonstrate dynamically and frame the photos.

According to the data provided by the teacher, can you calculate how long this photo frame is?

After the students work out the length of the photo frame, let them think: If you want to add another piece of glass to this photo, where should the glass be added? Combine the students' answers and demonstrate how to add glass to the photo frame dynamically.

Teacher: Great! The students did a great job! Let's look at the next question:

2. Teacher: Are the perimeters of these two groups of figures the same? Why? (Courseware is displayed separately)

(1) Show the method of moving according to the students' answers: their perimeters are equal. (translation)

(2) Their perimeters are not equal.

Fourth, class summary and extracurricular extension.

Teacher: If you want to add a lace to this round mirror, how can you measure how long the lace should be added?

Measure it with the tools in the envelope.

Method 1: I'll wind the thread first, and then measure it with a ruler. Pay attention to starting from the "0" scale. (demonstration)

Teacher: Try it. Is there any other way? If there is only one ruler, can you not generate energy?

Method 2: I make a mark on the circle, and then roll the circle on the ruler to know its circumference.

Teacher: It seems that the measurement method of circle is very clever. (Demo) If there are many tools, are there any other methods? Please find other ways after class.

Homework after class: Measure your head circumference and waist circumference after class, and talk with your partner.

(Courseware demonstration)

Teacher: Please recall this lesson. What did you get? (Student answers:)

The teacher is really happy for you. Not only do we know the circumference of a closed figure, but more importantly, we have explored a method to measure the circumference from our own activities. It is really not easy! This is inseparable from your unity and cooperation. Congratulations! I hope you can apply what you have learned and solve practical problems in your life.

Blackboard writing: perimeter

The length of a closed figure is its perimeter.

Just finished the open class, I hope it will be useful to you!