Analysis of learning situation:
The students in this class are lack of foundation and practical ability, so through the design of this class, they are given a chance to practice, hoping that this way can let them learn more and improve their practical ability.
Teaching objectives:
1. Knowledge and skills: Understand the stability of triangles and the instability of quadrilaterals; Will use the stability of the triangle to turn unstable graphics into stable graphics.
2. Process and method: By observing the geometric figures in examples, we can verify the stability of triangles and the instability of quadrangles, cultivate students' ability to appreciate the beauty of mathematics, and mathematize their lives. Knowing the advantages and disadvantages of triangle stability and quadrilateral instability, and applying them to real life, will turn unstable graphics into stable graphics.
? 3. Emotional attitude and values: Feel the mathematical problems in life, feel the aesthetic value of mathematics, feel the existence of mathematics in life, and feel the fun of learning mathematics.
? Teaching emphasis: what is the stability of triangle and its application in life.
? Teaching difficulties: judging whether a figure is stable or not and fixing an unstable figure.
? Teaching methods: teaching and cooperative inquiry.
? Teaching tools: multimedia courseware, homework paper, triangle and quadrilateral teaching AIDS, chair teaching AIDS.
? Teaching process:
First, review the old knowledge and introduce the situation.
? 1. What did we learn last class?
Default: the concept of triangle, height, bottom and representation of triangle.
? 2. Today, let's explore a big secret hidden in a common phenomenon-when building a house, before installing the window frame, carpenters often nail a batten on the window frame obliquely. Faced with this phenomenon, the teacher has a question: Why do carpenters do this?
Teacher: So today we will study this problem together and explore the hidden secrets.
? Second, create activities to impart new knowledge.
? 1. Do it yourself and explore the experience.
Teacher: Please form a triangle and a quadrilateral with splicing strips of equal length in groups of four. After finishing, you can communicate with the students in the group and see what you find.
? (Students' activities, teachers' inspection, understanding students' basic ideas and methods of solving problems, selecting typical cases to explain and answer students' doubts)
? Teacher: Which group reports to you? How many different triangles and quadrangles have you designed?
? Default: triangles are all the same shape; There are many kinds of quadrangles;
? Teacher: Observing our quadrangles, we find that each group of quadrangles made of splicing strips with the same length has different shapes. Why?
? Default: Because the angle changes, the shape will also change. In other words, our quadrilateral is variable (unstable).
? Teacher: Let's look at our triangle again. Are all the triangles in the class the same? Let's invite some students to come up, pick up your triangle and put it together for verification. (Call 3-5 students to show on stage)
? Teacher: These triangles are exactly the same shape. What's going on here?
? Default: Because the lengths of the three sides of a triangle are fixed, the size and shape of the triangle are also fixed.
? Teacher: Let's guess what characteristics a triangle should have.
? Default values: stability and uniqueness.
? 2. Observe the triangle in the graph and feel the connection between mathematics and life.
? Teacher: Students, look at the pictures below and see where there are triangles.
Play pictures of triangles in life. Students look for triangles in the pictures and think about the role of triangles in fixing and supporting these objects. )
? 3. Create a game to recognize the stability of triangle and the instability of quadrilateral again.
? Teacher: After reading so many pictures, we understand the role of triangle (uniqueness) stability in it. Is the triangle really that strong? Let's do an experiment to study this problem.
? Teacher: The teacher has prepared a quadrilateral and a triangle here. We asked two students to come up and play a game: pull these two numbers, and whoever can pull them out will win! You can guess first, who will win
? Default: the student who takes the quadrilateral wins.
Teacher: Why can't our triangle move when it is pulled, but the quadrilateral will deform when it is gently pulled?
? Preset: After the lengths of the three sides of a triangle are determined, the shape and size are determined, while the quadrilateral changes due to the angle change during the pulling process. (Because of the stability of triangles and the instability of quadrangles)
? Teacher: Then, we discussed a feature of triangle: stability.
? 4. Go back to the problem and solve it
? Teacher: Now let's solve the teacher's problem before class: when building a house, before installing the window frame, the carpenter often nails a piece of wood diagonally on the window frame first. Why did the carpenter do this? Who can answer this question through today's experiment and summary?
? Default: The quadrilateral is unstable. After nailing a piece of wood obliquely, two triangles are formed. The stability of the triangle can prevent the window frame from deforming.
? 5. Play the onion micro-lesson "Stability of Triangle" to feel the interpretation and application of triangle stability in life again and complete the quiz.
? Third, classroom exercises.
? Observe the graphics on the homework paper to see which graphics are stable and which are unstable, and make the unstable graphics stable by drawing lines.
? Quadrilateral, pentagon and hexagon.
? Fourth, class summary.
? What did you gain from today's study?
? V. Homework
? 1. Design an unstable graph with the knowledge learned today, and then turn it into a stable graph.
? 2. Find out the application of triangle stability in life, and then communicate with your deskmate.
? Sixth, blackboard design
? Characteristics of triangle
The quadrilateral is unstable.
Triangles are stable.