The expanded drawings of cuboids and cubes are the third unit of the fifth volume of Mathematics published by People's Education Press. The teaching objectives are as follows:
1. Let the students know the unfolded drawings of cuboids and cubes through activities such as operation and observation. They can find the opposite faces of cuboids and cubes in the unfolded diagram, and can judge whether some plane figures can be folded into cuboids and cubes.
2. Let students initially feel the mutual transformation between plane graphics and three-dimensional graphics, and develop their spatial imagination.
Course introduction:
It is a common problem in recent years whether a plane figure composed of six connected squares can be folded into a cube. The learning content in cuboid and cube is to develop students' spatial concept, while the plane expansion diagram is imagined from the shape of cube and the physical shape is imagined from the plane expansion diagram. The transformation between geometry and expansion diagram is an important aspect of spatial concept.
Reflections on the cognitive teaching of cuboid;
The design of this lesson begins with reviewing the original knowledge. Students have a preliminary understanding of the cuboid in the third grade textbook, so I arranged preview homework in advance, arranged for students to make cuboids and asked them to find the characteristics of cuboids from three aspects: face, edge and vertex. In the teaching process of example 1, the characteristics of cuboid are supplemented and perfected by combining the physical objects and the findings of students' preview, which is beneficial for students to learn the content of this lesson and this unit.
In the teaching process, students should be guided to see, touch and measure the surface of a cuboid intuitively. By using the stick in the learning tool, students can find that the two surfaces will be square under special circumstances. Make use of the link of group cooperation to spell out the opposite faces, so that students can understand that the opposite faces are exactly the same, so that students can perceive that 12 edges can be divided into three groups according to their length, and four edges in each group are opposite and equal in length. In the process of hands-on operation and mutual discussion, students deeply understand the characteristics of cuboids and experience the fun and sense of accomplishment of learning. After intuitive observation and operation, the teacher taught the drawing method of straight view again, and introduced the drawing method of cuboid from an intuitive object, so that students can know that cuboid can only see three faces because of the angle of view, so as to understand why they draw perspective views like this, and strengthen their proficiency in drawing straight views through practice. In the following "class exercises" and "class summary" sessions, teachers use the forms of students doing problems and teachers' comments to let students see their own shortcomings more clearly, so as to make use of their spare time to check and fill gaps and learn better.