Level a

Abstract the angle from three-dimensional graphics and describe it in your own language.

Class b

The angle is redefined through geometric transformation.

Class c

Combined with intuitive operation activities, understand the method of comparing angles.

The first plate: perception angle

1. Compare spheres with cubes and cuboids. A sphere has no angles, while other three-dimensional figures have angles.

2. Compare the circle and polygon (rectangle, square, other polygons), and distinguish from the plane that the circle has no angle and other figures have angles.

3. What is a horn?

Let the children touch it, draw a picture, and abstract the angle from the plane three-dimensional figure.

Teacher: What's the difference between comparing balls and cubes or cuboids?

Health: the ball can roll, but other three-dimensional graphics can't roll.

Teacher: Why can a sphere roll?

Health: Because it has no horns.

Health: I think the ball has no angle, while other three-dimensional figures have angles.

Teacher: That's good!

Teacher: What's the difference between comparing circles and polygons (rectangles, squares, other polygons)?

Health: A circle has no corners, while other figures have corners.

Teacher: Then what is a horn?

Health: That sharp place.

Teacher: Can you point with your finger?

Health: Yes. (In fact, he refers to a point on the picture. )

Teacher: Do you think this is a corner? Ok, the teacher puts him on the blackboard now. Please look carefully. Is he a corner?

Health: It seems to be a point, not an angle.

Teacher: Then what is a horn?

Teacher: If you want to be a corner, what is missing?

Health: two lines are missing! ! !

Teacher: Do you think this is a horn? (Select an angle from the chart)

Health: Yes.

Teacher: Let's see what these corners have in common.

Health: Everyone has a sharp place and two straight lines.

? The second plate: architectural angle

1. Explore the characteristics of angles through geometric transformation.

Points and lines will never change, and openings will always change.

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An angle consists of a vertex and two straight sides.

3. Find corners in life and graphics.

Teacher: The teacher made an active angle according to the characteristics of the angle. Now let's see what has changed and what hasn't.

When I rotate, I rotate an acute angle, a right angle, an obtuse angle and a straight angle respectively. )

Health: During your rotation, the points and lines do not change.

Teacher: So what has changed?

Health: the distance between two lines.

Teacher: That is to say, in the process of rotation, the opening of the angle has been changing.

Teacher: The points and lines have not changed during the rotation of the angle. Can you name them?

Health 1: tip

Health 2: Canon

Health 3: Vertex

Health 3: Corner

Teacher: These names are very good. Mathematically, we call it the vertex. Can you also name these two lines?

Health: Advantage

Teacher: I like this name very much, so please observe what these two sides look like.

Health: Straight man.

Teacher: Yes, it's two straight sides. In other words, an angle consists of a vertex and two straight sides.

Teacher: Here are some figures. If you think they are angles, please put forward the number "1". If not, please increase the number "2".

Health: 1

Health: 2

Teacher: Why?

Health: It has a curved side and should be straight.

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Health: 2

Teacher: Why?

Health: Not an angle without a vertex.

Health: 1

Teacher: Where is the corner in our life?

Health 1: in the math book.

Student 2: On the blackboard.

Health 3: door

Health 4: Table corner

Health: No, the corners of the table are round and have no vertices.

Teacher: In life, in order to avoid danger, we make some table corners round. I call them corners because they are just corners in life, not corners in mathematics.

Ok, let's look for the corner in the picture again.

? Part 3-Practice

Thinking:

A square has four corners. If you cut off a corner with scissors, how many corners are left?

Health: negative one angle, of course, three angles.

Teacher: Why?

Health: 4 minus 1 equal to 3.

Teacher: So, does cutting one corner mean three corners? Everybody take out the horns in your hands and verify them together.

Health: Hey, how did it become a Pentagon after it was cut?

Teacher: Can you show us your cutting process?

Health: After I cut one corner, there are still four corners left, and the number of corners has not changed.

Teacher: Come on up and let everyone open their eyes.

Student: Teacher, I cut three corners.

Teacher: Then you can also show us your cutting method.