Instructional Design and Instructor: Yang Jing, Lixian 054.

Teaching content: The classification of teaching material analysis (1) triangle in the second volume of the fourth grade of People's Education Press, and the teaching materials are arranged in two levels. The first level, according to the angle, know acute triangle, right triangle and obtuse triangle; The second level, according to the edge, know the special triangle: isosceles triangle and equilateral triangle.

(2) Generally speaking, the basic principle of classification is not to repeat or omit. Classifying triangles according to their angles conforms to the above principles. In the teaching material, the set diagram is used to intuitively express the whole and partial relationship between the whole set of triangles and acute triangle, right triangle and obtuse triangle.

(3) Triangles can be divided into equilateral triangles and isosceles triangles according to their sides. An isosceles triangle contains an equilateral triangle. However, it is difficult to classify by edge. In order to avoid increasing students' burden, the textbook does not emphasize the classification, but focuses on guiding students to understand the characteristics of edges and angles of isosceles triangles and equilateral triangles. Analysis of learning situation Students have already learned triangles in the first grade, and they also have a rich perception of triangles in their daily life. At the same time, the fourth-grade students already have certain logical thinking ability and spatial imagination ability. However, their logical thinking and spatial imagination are still incomplete and have certain limitations. At the same time, because students have just started to contact triangles, their understanding of the characteristics of some triangles is still superficial. Therefore, in teaching, I seize the valuable activity of classifying triangles, guide students to operate, classify triangles in schoolbags and explore classification methods. The teacher who teaches this course seems to have a feeling that in the process of exploring triangle classification, students can easily accept the content of classifying triangles according to the size of triangle angles, and it is not easy to enter the level of classifying triangles according to triangle edges. For this problem, in class, I first changed the presentation of knowledge to conform to students' cognitive rules, classified the triangles under the two standards together, and focused on angle division, so that students could find the characteristics of acute triangle, right triangle and obtuse triangle, and then let students take a look at what new discoveries were made with the help of tools in their hands, so that students could find isosceles triangle and equilateral triangle, and then they could master the edge characteristics of triangles unconsciously.

Teaching objectives:

1, through the process of classifying triangles by hands-on, let students know and identify acute triangles, right triangles, obtuse triangles, isosceles triangles and equilateral triangles, and understand the characteristics of various types of triangles.

2, through observation, comparison, classification, cultivate students' observation ability and thinking ability.

3. Cultivate students to learn cooperative learning through group cooperative inquiry. Teaching emphasis: understand acute triangle, right triangle, obtuse triangle, isosceles triangle and equilateral triangle, and understand the characteristics of each type of triangle.

Difficulties in teaching: Understand and master the characteristics of various triangles. Teaching preparation: several triangular cards

Teaching process:

1. passionate introducer: classmates, can you classify the existing people in our classroom according to certain standards? Teacher: Just now, we classified the people in the classroom in different ways, so if you look closely at the triangle family we just met, you will find that their angles are different and the lengths of their sides are different. In this lesson, we will classify triangles together. Supplementary topic: classification of triangles.

Second, explore new knowledge.

1. Determine the standard and define the target Teacher: (Six triangles are displayed on the blackboard) Please look at these triangles carefully. Do you think the angles of each triangle are the same? Are the edges the same? Can you be specific?

2. Study the classification standard.

Teacher: The students watched carefully! That's true. So how are you going to classify them? Think independently first and then communicate with each other at the same table.

Teacher: Who can tell us what you think? Teacher: What you said is really good. You can classify these triangles according to their characteristics. Teacher: Who else has different ideas? Teacher: You watched carefully. You can also classify these triangles according to the characteristics of the edges.

3. Explore in groups and get a new teacher: The following students can use the triangle provided by the teacher to choose a classification standard in the way of deskmate cooperation. They can use protractor, ruler and other tools to classify these triangles. Let's get started. Students at the same table do triangle classification activities. )

4. Show the results and reveal the rules (1) Know acute triangle, right triangle and obtuse triangle Teacher: Have you divided the students? Please report to the front and show how to classify triangles according to the characteristics of angles. Guide students to record and sort out that all three angles are acute (1)(4)(6) Two angles are acute and one angle is right.

(2)(7) Two angles are acute and one angle is obtuse. Teacher: The students did a good job. They divided triangles into three categories according to their angles. Which group of students did this? Teacher: Your thinking is clear. In fact, it is also classified according to the characteristics of triangle angle in mathematics. That will give full play to your imagination and give these triangles a name. Teacher: You have given a good name to each triangle gas. Triangle is divided into acute triangle, right triangle and obtuse triangle according to its angle. So who can talk about the characteristics of each type of triangle? _ Teacher: We can use set diagram to represent the relationship between these triangles. All triangles are regarded as a whole and represented by a circle. (Draw a circle) It seems to be a big family, because the triangle is divided into three categories, which seems to include three small families. (complete the setting diagram while talking. ) Every triangle is a part of the whole. On the contrary, these three triangles just constitute all triangles.

(3) A triangle must have at least two acute angles, so judging the type of triangle depends on its maximum internal angle ... Teacher: Are there any other divisions? 3 according to the edge situation:

(1) I found two equilateral triangles and three equilateral triangles.

(2) Teacher: We call a triangle with two equal sides an isosceles triangle. Two equal sides are called waist and the other side is called bottom. (3) Teacher: A triangle with three equilateral sides is called an equilateral triangle.

(4) Measure the angles of isosceles triangle and equilateral triangle respectively. What did you find?

(5) Find out where these two special triangles are from the red scarf, triangle and slow sign. Teacher: We classify triangles according to different standards through observation and thinking. You are really something. The teacher will test you.

Third, consolidate the exercises:

1. True or false. Students are really picky and accurate in judgment. Keep trying.

2. I will make up for it

3. Guess, (You can judge whether it is an obtuse triangle by exposing an obtuse angle, a right triangle by exposing a right angle, and you can't judge what type it is by exposing an acute angle. All three types of triangles are possible. )

Fourth, class summary.

Five, the blackboard design