1. Through observation, operation and comparison, we will classify triangles according to the characteristics of their angles and sides and master the characteristics of various triangles.

2. Infiltrate the mathematical ideas of classification and set in activities, cultivate students' hands-on operation ability and inductive generalization ability, and further develop students' spatial concept.

3. In the process of triangle classification, communicate knowledge and cultivate students' awareness of inquiry and cooperation.

Emphasis and difficulty in teaching

Teaching focus:

Triangles are classified according to the characteristics of corners and sides.

Teaching difficulties:

Master the characteristics of various triangles.

teaching tool

Ppt courseware

teaching process

First, create situations and review old knowledge.

1, guess, review old knowledge

Teacher: Do you like guessing games, children? Today, the teacher brought us a riddle. Guess.

Courseware demonstration:

Shaped like a mountain,

The performance of stability is firm.

The three electrodes are connected end to end,

Learning is not easy.

Type a geometry.

The teacher asked: Good guess! How did you guess?

2. Review the classification of angles.

Show three kinds of angles between classes for students to identify.

3. Introduce and reveal the theme

Teacher: A triangle has three angles and three sides, and its stability is widely used in daily life. Observe the characteristics of these triangle angles and fill in the blanks. (Title on the blackboard: Classification of Triangle)

(design intent: interesting question and answer, quote? Healthy? Enter victory. Through the quiz, arouse students' intentional attention to the corners and sides of the triangle and activate their enthusiasm for learning. At the beginning of class, fun is born? . )

Second, practice and explore classification

(a), according to the angle.

1, Teacher: Kid, can you divide the following triangles into three categories according to the characteristics of the angles? Put them in the box.

2. Hands-on operation and independent exploration.

3, the group report exchange, evaluation.

4. Report of the representative of the Group.

Teacher: How many categories is your group divided into? Which belong to the same category? What are the characteristics? Are there different divisions?

5, courseware display, and named according to the characteristics of various triangles.

6. To sum up, the teacher introduces the set diagram of triangle divided by angle and writes it on the blackboard.

7. Consolidate exercises

(2), according to the edge

1, Teacher: Teacher, here is a triangle (showing an isosceles triangle). Please observe it. What are the characteristics of its side? (There are two equal sides) How do you judge? How many ways are there? What about this triangle? (Show equilateral triangle) How to judge? (Folding) Who can show you! Very good. Let's take out another set of triangles to think about. Can you classify the edges according to their characteristics?

2. Think independently first, and then cooperate in groups.

3, the whole class report exchange, evaluation.

4, courseware display, and named according to the characteristics of various triangles.

5. Know the part names of isosceles triangle and equilateral triangle, and the relationship between the two bottom angles of isosceles triangle and the three inner angles of equilateral triangle.

6. Think about it. Is an equilateral triangle an isosceles triangle?

7. practice. Find the triangle in the picture and say what triangle it is.

7. summary.

(design intent:? The process of autonomous learning is actually the process of teaching activities? . Promoting learning through activities is the teaching direction of this section. In the activity, give students enough time and space to explore the generation process of mathematical knowledge freely and openly. By looking, thinking, discussing, scoring, guessing and other forms of learning, more can be provided for students? Mathematical dialogue? Opportunity, and strive to make students really move, fully demonstrate learning by doing, so as to understand the characteristics of triangles, and then learn to classify triangles, promote students' ability of classification, generalization, reasoning and hands-on operation, make them realize the true meaning of mathematics in the process of activities, gradually develop the habit of exploration, and cultivate students' sense of cooperation and innovation. )

Third, consolidate exercises and improve internalization.

1, fill in.

Step 2: repeatedly

judge

Fourth, the whole class summarizes and extends after class.

1. What did you gain from this class? Tell me about it!

Step 2 think about the problem

Triangular classification teaching plan (2) teaching objectives

1. Knowledge and skills

Through student activities, help students understand the method of triangle classification by angle and master the concepts of right triangle, acute triangle and obtuse triangle; Know isosceles triangle, equilateral triangle. Cultivate students' observation ability, hands-on operation ability and abstract generalization ability; The concept of development space.

2. Process and method

Make students experience the process of observation, operation, comparison and generalization, and realize the characteristics of each type of triangle angle in classification; Find the characteristics of the edge. Infiltrate the idea of set.

3. Emotions, attitudes and values

Stimulate students' awareness of active participation, make students feel the joy of success and enhance their interest in learning.

Emphasis and difficulty in teaching

Teaching focus

Concepts of right triangle, acute triangle, obtuse triangle, isosceles triangle and equilateral triangle.

Teaching difficulties

Discover the characteristics of triangle corners and sides.

teaching tool

Ppt courseware

teaching process

I. Introducing new courses:

Teacher: Today, the teacher brought some children to everyone. They want to play games. Can you group them according to different standards? There are some pictures of children in the courseware. After the observation, the students are grouped according to different standards, and then the teacher points out the courseware summary. Today, the teacher also brought some triangular friends (different triangles are shown in the courseware). Do you want to know what they said?

Student: Thinking (Trigonometric Statement Showed by Courseware)

Teacher: It turns out that they want their classmates to help. Are you willing to help them?

Health: Yes.

Teacher: In this class, we will learn the classification of triangles together. (Triangular classification of blackboard writing topics)

2. Explore new knowledge

(1) Teacher: Who will get up and read? (Courseware demonstration group cooperation requirements) Students' reading requirements. Teacher's comment: Your voice is really loud.

Teacher: Next, please take out your learning tools, carefully observe the sides or corners of the triangle and classify them.

(2) Students cooperate in groups.

(3) Students' statements and communication.

Teacher: Did you divide it? Who can tell us how your group is divided?

Student: Our group is divided by angle. No.2 and No.4 have a right angle, and the other two are acute angles, so they are grouped together. No.3 and No.5 have an obtuse angle, and the other two are acute angles. No.65438 +0, No.6 and No.7 are all acute angles, which are divided into three categories. We divide them into three categories according to their angles.

Teacher: What you said is really complete. Who wants to talk? I speak better than him.

Health: Our group is also divided into three categories according to the angle. No.2 and No.4 are right angles, and the other two are acute angles. No.3 and No.5 have an obtuse angle, and the other two are acute angles. 1, 6 and 7 are all acute angles.

Teacher: Who will comment on what he said?

Health: complete and loud.

Teacher: Just now, the two groups were divided by angle. Are there any different classification methods? Somebody say something.

Health: Our group is divided according to the length of the side. No.2, No.3 and No.7 are divided into one category, with three unequal sides, No.4, No.5 and No.6 have two equal sides, andNo. 1 has three equal sides. We are divided into three categories.

Teacher: You said what your group thought. Just now, the students classified triangles according to different standards. Next, let's study the angle.

1. Divided by angle

Teacher: Just now, we divided No.2 and No.4 into one category, one of which is a right angle and the other two are acute angles. We call this triangle a right triangle. The teacher writes on the blackboard in a right triangle. (The courseware shows the definition of right triangle) Then tell the students what a right triangle is. The teacher gave an appropriate evaluation.

Teacher: We divide No.3 and No.5 into one category, in which one angle is obtuse and the other two angles are acute. We call this triangle an obtuse triangle. The teacher writes on the blackboard with an obtuse triangle. Who can say what an obtuse triangle is? The courseware shows the definition of obtuse triangle. The teacher gives appropriate comments.

Teacher: We classify the angles of No.65438 +0 and No.6 and No.7 as acute angles. We call this triangle an acute triangle. The teacher's blackboard is an acute triangle. Who can tell me what an acute triangle is? The courseware shows the definition of acute triangle. The teacher gives an evaluation.

Teacher: I want to ask the students, if you carefully observe these three types of triangles, how many acute angles do each type of triangle have?

Health 1: Each triangle has at least two acute angles.

Teacher: That's his idea. Who wants to talk?

Health 2: I also think that each triangle has at least two acute angles.

Teacher: Just now, they all thought that each triangle had at least two acute angles. Do the students agree with them?

Health: I agree.

Teacher: Through our careful observation, we found that a triangle has at least two acute angles. Then we say that triangles can be divided into three categories according to their angles: right triangle, obtuse triangle and acute triangle. The courseware shows the assembly drawing.

2. Courseware shows exercises.

3. Teacher: Just now we studied how to divide by angle, and then we went on to study how to divide by edge.

According to the edge division

① Know isosceles triangle and equilateral triangle.

Teacher: Just now we divided No.2, No.3 and No.7 into one class, No.4, No.5 and No.6 into one class of equilateral, 1 into one class of equilateral. We call the triangle with unequal sides No.2, No.3 and No.7 an equilateral triangle, the triangle with equal sides No.4, No.5 and No.6 an isosceles triangle, and the triangle with equal sides is called its waist and opposition. The angle between the two waists is called the top angle, and the angle between the waist and the bottom is called the bottom angle. When all three sides are equal, such as triangle 1, we call it equilateral triangle, and it also has a name called regular triangle (courseware demonstration). Next, I want to ask the students that an isosceles triangle has two equilateral sides and an equilateral triangle has three equilateral sides. Do you think an equilateral triangle is an isosceles triangle?

Health 1: An equilateral triangle is an isosceles triangle.

Health 2: I also think an equilateral triangle is an isosceles triangle.

Teacher: Do you agree?

Health: I agree.

Teacher: Because as long as two sides are equal, it is an isosceles triangle, and all three sides of an equilateral triangle are equal, then every two sides are equal, so we say that an equilateral triangle is a special isosceles triangle (as demonstrated in the courseware).

Teacher: Who can give an example? Where is the isosceles triangle in our real life?

Health 1: red scarf

Health 2: Triangular ruler

② Explore the characteristics of isosceles triangle and equilateral triangle angle.

Teacher: There are many such triangles in our life. The characteristics of equilateral triangle and isosceles triangle that we just learned, the two bottom angles of isosceles triangle and the three angles of equilateral triangle, still have secrets. Please take out the isosceles triangle and equilateral triangle in your hand and find them quickly.

(3) group cooperation to explore the secret.

4 summary of the exchange report: Teacher: It's really amazing. The students found that the two base angles of an isosceles triangle are equal and all three angles of an equilateral triangle are equal.

5. Teacher: The students speak very well, so how did they master it?

3. Consolidation exercise: (Courseware display exercise)

Appreciation: Teacher: The students have a good grasp. Next, please enjoy the isosceles triangle in life. (Courseware shows music appreciation)

Verb (abbreviation of verb) summary: talk about harvest.

Write on the blackboard.

Classification of triangles

Acute triangle, equilateral triangle

Divide the right triangle by the angle and then by the edge.

Obtuse triangle isosceles triangle (equilateral triangle)