Subject mathematics teaching object: Class 4, Grade 4 students.
Textbook Version People's Education Edition Grade/Album Number Grade Four Volume Two
I. teaching material analysis
The sum of the inner angles of a triangle is the content on page 68 of Unit 5 in Volume 8 of People's Education Press, which belongs to the knowledge point of "Graphics and Geometry" in the second phase of primary school and is an inquiry course. Before, students have mastered the classification and measurement of angles, the characteristics and classification of triangles, and have an intuitive understanding of triangles. This lesson is for students to explore and discover the important property that the sum of the angles in a triangle is 180. Learning this lesson well will help students understand the relationship between the three internal angles of a triangle, lay an important foundation for studying the internal angles of polygons and accumulating geometric knowledge in the future, and provide an effective way for further developing students' spatial concept.
Second, the analysis of learner characteristics
The fourth-grade students are: 1, * * * The fourth-grade students have mastered the knowledge of angles, including drawing angles, spelling angles, measuring angles, classification of angles, and degrees of internal angles of triangles; Know the triangle, understand its characteristics and classification; I have accumulated some experience in corner painting and corner spelling, and have certain teamwork ability and hands-on operation ability; Have a preliminary spatial concept and geometric intuitive ability. 2. Personality learning ① (There are still students) who can't measure angles and readings correctly with a protractor. (2) The experience of "corner matching" activity is insufficient, and it is easy to ignore key operations such as "vertex-to-vertex". (3) Through the small investigation before class, we know that some students have never taught the prophet, and know that "the sum of the angles in a triangle is 180", but they have a little knowledge.
Third, teaching objectives (knowledge and skills, mathematical thinking, problem solving, emotional attitude)
1. Knowledge and Skills Students can understand and master the sum of the internal angles of a triangle as 180 by exploring the process of the sum of the internal angles of the triangle. 2. Mathematical thinking In the operation experiment, the mathematical thought of "transformation" was infiltrated, and the scientific exploration method of "from special to general" was experienced. 3, problem solving, using the knowledge of triangle internal angle sum to solve practical problems. 4. Emotional attitude in learning activities, improve learning ability, and cultivate students' mathematical literacy such as cooperative consciousness, practical ability and logical reasoning ability.
Four, teaching focus, difficulty and teaching focus
1, the focus of teaching is to understand and master that the sum of the interior angles of a triangle is 180. 2. Teaching difficulty: the sum of the angles in the triangle is 180. 3. Teaching Keys Most students knew before class that the sum of the interior angles of the triangle was 180, but they didn't know its verification process. The focus of this lesson is to guide students to experience the whole process of guessing, verifying and inducing through hands-on practice, personal perception and collective communication, and to provide research methods for students to learn mathematics and other disciplines in the future.
Verb (abbreviation of verb) teaching environment and resource preparation
According to the pre-class survey, most students can use protractor to measure angles correctly, but they are not skilled in the operation of "spelling angles", and it is easy to ignore the specific operations such as "vertex to vertex, edge to edge". At the same time, most students already know that the sum of the internal angles of the triangle is 180, but they don't know the origin of the conclusion. While fully understanding and respecting the teaching materials, we should combine the characteristics of inquiry practice class. I will prepare the following materials (triangles, etc.) before class. ), and ask students to make triangles of different types and sizes (including acute triangle, right triangle and obtuse triangle) in groups before class. In addition, I will ask students to prepare relevant learning tools and review relevant knowledge, including measuring angle and spelling angle. The purpose is to understand the real starting point of students and make full preparations for exploration.
Teachers prepare before class and students prepare before class.
Triangular plate protractor ruler hand scissors (several sizes) acute triangle (several sizes) right triangle (several sizes) obtuse triangle multimedia courseware geometry drawing board a pair of triangular plates, hand scissors, math book acute triangle, right triangle and obtuse triangle (several kinds each)
Small research before class 1, measure it. The size of this angle is (). 2. Fight. Can you spell the following angles with a set of triangles? How do you spell it? (1)105 (2)120 (3)1803. According to the degree of angle, triangles can be divided into (), () and (). 4. A triangle has () angles. Do you know the sum of their degrees? Why?
Sixth, the choice of teaching strategies.
"Mathematics Curriculum Standard" points out: "Effective mathematics activities can't rely solely on imitation and memory, and hands-on practice, independent exploration and cooperative communication are important ways for students to learn mathematics." In this class, according to the age characteristics of the fourth grade and the characteristics of the content of this class, I adopted interesting teaching method, guided discovery method, cooperative exploration method and intuitive demonstration method under the inquiry teaching mode, so that students can practice in "nonlinear" group cooperative learning, innovate in observation and exploration, and strive to achieve the best combination of teaching method and learning method.
Seven. teaching process
Design Intention and Resource Preparation of Teachers' Activities and Students' Activities in Teaching
The first link: introduction, setting up doubts and guiding the new 1, who is right or wrong? (1') Teacher: In a triangular family, there are three brothers. They have always been United and friendly, but today they quarreled over a trivial matter. Listen. Teacher: Do you know what they are arguing about from the conversation just now? 2. Know the sum of the interior angles of the triangle. (1')( 1) What is the interior angle of a triangle? (2) What is the sum of the internal angles of a triangle? (3) Who has the largest sum of internal angles among the three brothers? 3. Lead the topic. 1. Students watch the animation and tell who the "three brothers" are arguing about. 2. Students use their own language to understand the concept of the interior angle and the sum of the interior angles of a triangle. At the same time, students are asked to comment on which of the "three brothers" has the largest internal angle. 1. Design intention: Through the courseware, vividly demonstrate the "internal angle sum" dispute between "triangle families", so as to launch a series of subsequent guessing exploration experiments, which greatly stimulate students' enthusiasm for knowledge. 2. Design intention: Let students talk about what is the internal angle and time with their own understanding, which not only cultivates students' ability to understand concepts intuitively; It also plays the purpose of tapping students' potential, that is, how to find the sum of the internal angles of the triangle with the learned method.
Design Intention and Resource Preparation of Teachers' Activities and Students' Activities in Teaching
The second link: hands-on operation, exploring new knowledge. This link is divided into five steps: 1, and a guess is put forward. (3') Show the mathematical tool that students are familiar with-the triangle. By observing the sum of the internal angles of these two triangular plates, guide the students to guess: the sum of the internal angles of all triangles is 180. 2. Explore and verify. (17') Activity 1: Make a plan. Take the group as the unit, make the verification plan, and report to the team leader. (3') (Note: Teachers patrol each group to understand students' ideas, and prompt the group that can come up with cutting and spelling in time, "If you don't cut out the three inner corners of the triangle, can you put the three inner corners together?" Activity 2: Practical operation (8') Requirements: (1) Use the triangle in the stationery bag and choose the favorite method to verify the conjecture. (2) After the verification, please talk about how you verified in the group and what your conclusion is. (3) The team leader collects the research results and prepares the report. 1. Students observe the sum of the internal angles of two triangles and reasonably guess: Are the sum of the internal angles of triangles all 180? 2. Students explore together and verify the conjecture. Activity 1: The team * * * formulates the verification scheme. Preset 1: Measurement Preset 2: Cutting and Spelling Preset 3: Folding and Spelling Activity 2: Students begin to test their guesses. You may come up with some verification methods, such as measuring, cutting and folding. Communicate the results in the group. 1, design intent: It will take a long time to guess by drawing, measuring and calculating in practical teaching materials, and observing the internal angles and degrees of triangles that students are familiar with can also help students learn to guess reasonably and master special to general logical thinking methods. 2. Design intention: The group determines the verification scheme through discussion, so as to enrich the problem-solving strategies and cultivate students' thinking of solving problems through modeling. At the same time, students are given enough time and space to discuss, practice, guide and show, and bilateral activities between teachers and students are integrated. In a series of experiments and operation activities, I have accumulated some experiences and methods to understand graphs, and formed a preliminary understanding of the verification that the sum of the internal angles of a triangle is 180.
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