Teaching content:

Example 1 and example 2 on pages 85-87 of the science book, and then practice, practice 13, topic 1~3.

Teaching objectives:

1. Make students feel and discover the basic characteristics of a circle in activities such as observation, drawing and discussion, and understand the significance of the center, radius and diameter of a circle; Will draw a circle of a specified size with compasses; Can explain some daily life phenomena with the knowledge of circle.

2. Enable students to further accumulate experience in understanding graphics, enhance the concept of space and develop mathematical thinking.

3. Make students further experience the connection between graphics and life, feel the learning value of plane graphics, and improve their interest in mathematics learning and confidence in learning mathematics well.

Teaching process:

First, the introduction of new courses.

1. Game: Touch graphics.

Show me the bags with rectangular, square, parallelogram, triangle, trapezoid and round pieces of paper.

Make a request: Do students like playing games? The teacher brought a bag with many flat figures in it. Let one student touch them in turn, and the other students say the names of the figures together.

2. Show the round paper touched by the students and point out that it is a round paper (blackboard writing: circle). What's the difference between a circle and the triangles, rectangles and other polygons we have learned before? What are its interesting features? Let's study these problems together in this class.

Understanding of the circle.

Second, teaching examples

1. Question: Have you ever seen a circle in your life? For example.

When students communicate, pay attention to the following points: first, if the round object mentioned by students is around, let them point to the circle on the object; Secondly, some typical round objects or pictures of different sizes should be prepared before class. When students talk about these objects, they can present them in time. Thirdly, if students regard the ball as a circle, they can know that the ball is a three-dimensional figure and the circle is a plane figure through comparison.

2. Follow-up: After talking so many times and watching so many times, do you want to draw a circle? Think about it first, then draw a picture with the tools at hand.

3. Students draw circles independently. When organizing communication, we can introduce some typical painting methods in combination with the painting methods listed in the textbook. If some students want to draw a circle with compasses, don't rush to let them tell the specific operation process.

4. Enlightening thinking: What is the difference between a circle and a polygon such as a triangle or rectangle that I have learned before?

In communication, the camera made it clear that the rectangle, square, triangle, parallelogram and trapezoid I learned before are all surrounded by line segments, while the circle is a figure surrounded by curves.