In the first class, through observation and operation, students can intuitively understand the common plane graphics such as rectangle, square, triangle, parallelogram and circle, know the names of these graphics, and identify and distinguish them. In order to stimulate students' interest in learning, we draw lessons from teacher Hao Lei's picture book class, and integrate the mathematical picture book The Watermelon Thief into the teaching of "Understanding Graphics", so that students can further perceive the process of "face" in "body".
The hot summer is long, and everything is competing to grow. There is a quiet and peaceful village in the dense forest. The villagers here are a little special, because they are all three-dimensional figures with a bottom and edges.
There is a ball in the hut on the west side of the village. The ball always feels different in the kingdom of three-dimensional graphics. Very lonely.
Teacher: Why does the ball feel different and lonely?
Because other three-dimensional graphics have bottom surfaces and sides, some graphics also have edges and vertices. It happened that there is only a ball, which is round from any angle, just a ball, so it is very lonely.
As the story continues, ...
But the ball is hardworking. It takes care of a fertile land where many sweet and juicy watermelons are planted. Every day, the ball is trying to water, fertilize and catch insects for watermelon ... The weather is getting hotter and hotter, and watermelon grows day by day. Surprise ball. Yes, every watermelon looks more and more like itself. It is round from any angle. Watermelon is like a ball's friend. The ball says to them every day, little watermelon, like me, you have no bottom. You must be careful. It is easy to fall off when you roll around. ...
Bauer cherishes his watermelon very much. The first thing he does when he gets up every day is to water them.
Early this morning, Xiaoqiu came to the watermelon field, but he was too scared to speak by the sight before him. Some watermelons rolled to the east, some rolled to the west, some were broken, and many watermelons were missing.
The ball said angrily, "melon thief, I must find you and show you!" "
But how can we find the melon thief? When the ball was angry and anxious, he suddenly found some footprints in the watermelon field that he had never seen before.
Son, would you like to help the police uncle solve the case?
Our class forms a small detective team to assist in handling the case, but the small detective must be justified!
There are criminal footprints on the watermelon ground, as shown in the figure below.
Teacher: This is a footprint found by the police uncle at the crime scene. Do you have any good suggestions or ideas after seeing this clue?
Health: I think it may be a cube or a cuboid with a square surface.
Teacher: What is the reason?
Health: Because they can all print square footprints.
Teacher: Everyone expressed their inference and explained the reasons. Is it true?/You don't say. We need to do an experiment to verify it.
Students use the prepared three-dimensional graphics mold and inkpad to complete the verification process on the task list.
Teacher: According to the footprints left by criminals, who do you think is the melon thief now?
Health: Cubes and cuboids.
Teacher: Remind me, teacher, what happens when the post is turned over?
Health: Wow! Shorter volumes will leave rectangular footprints, longer volumes will become square footprints, and longer volumes will become rectangular footprints.
Health: It turns out that the suspect may be a cuboid, a cube or a cylinder.
The police found the sideways marks left by the criminal when he fell. As the picture shows, detectives, who is the real criminal?
Teacher: What do you think when you see this?
Health: It's a side of a cuboid. One side of it is square and the other side is rectangular, so it leaves a square footprint and a rectangular footprint. Combining the two clues, the criminal must be a cuboid.
Student: No, it left a square footprint when it stood, and a side footprint after it fell. This rectangle is long, and it is a combination of rectangle and square.
Health: It may even be a cylinder. Roll for a while.
Student: No, if it is a cylinder, it should only leave a long rectangle, or a circle, and it will not produce a square.
Health: It may even be a square. When two squares are put together, it is a rectangle.
Teacher: What you said is very reasonable. Let's use molds and inkpad to verify its falling process.
Teacher: Now that the cylinder has been ruled out, is the criminal a cube or a cuboid?
Student: Draw a line from the middle of the rectangular footprint of clue 2 to see if it can be divided into squares with the same size, and then you can judge whether it is a cube.
Teacher: Very clever. Let's check again.
Health: Haha, the criminal is not a cube, but a cuboid.
Teacher: Congratulations, you caught the real criminal with your wisdom.
Guess what will be the end of the story if the criminal is found?
The students' imagination is very rich, and the general conclusion is as follows.
This lesson keeps the story line in the original picture book, so that students can focus on the main problem of "catching melon thieves" through rubbings, so that we can understand the relationship between three-dimensional graphics and plane graphics and perceive "face on the body"
In the story, the triangular pyramid of the melon thief was replaced by a cuboid familiar to children. According to the characteristics of the cuboid, the children asked the suspect to expand his footprints and finally caught the melon thief.
At the end of the story, let the students continue to make up stories and let the children play their imagination and creativity.
"Taking children to heart" is not only a goal, but also an action. Give your child two clues, and the child can convince you with reason.