Comments on the teaching plan of the second volume of the sixth grade mathematics circle courseware;
In the form of game introduction, education is entertaining, that is, to perceive the formation process of the circle, infiltrate the fixed thinking, initially understand the essentials of drawing the circle, and draw closer the feelings between teachers and students. According to the characteristics of geometry knowledge and children's cognitive rules, various senses participate in learning and practice activities by looking, thinking, speaking, drawing and discussing. He not only changed his understanding of the circle from perceptual to rational, but also developed his spatial imagination, hands-on operation ability and oral expression ability.
Teaching objectives
1. Let the students know the names of the circle and its parts.
2. Make students master the characteristics of a circle and understand and master the relationship between radius and diameter in the same circle.
3. Initially learn to draw circles with compasses to cultivate students' drawing ability.
4. Cultivate students' thinking ability of observation, analysis, abstraction and generalization.
Teaching focus
Understand and master the characteristics of circles, and learn how to draw circles with compasses.
Teaching difficulties
Understand the concepts on the circle and summarize their characteristics.
teaching process
First, pave the way for pregnancy
(A) teachers use projection to show the following graphics.
1. The teacher asked: What plane graphics have we learned before? What is around these figures?
2. The teacher pointed out: We call this kind of figure a straight line on the plane.
(2) Teacher demonstration
A small ball tied with a rope. The teacher pulled at one end of the rope and threw the ball up.
1. Teacher's question: What figure do you think the ball draws? (The ball drew a circle)
2. Summary introduction: (showing the circle surrounded by iron wire) This is a circle. A circle is also a plane figure. In this lesson, we will learn the understanding of the circle. (Title on the blackboard: Understanding of Circle)
Second, explore new knowledge.
(1) The teacher asked the students to illustrate which objects around them have circles.
(2) Know the name of the part of the circle and the characteristics of the circle.
1. Students take out round learning tools.
2. Teacher: Touch the edge of the circle. Is it straight or curved? (curved)
The teacher explained that a circle is a curved figure on a plane.
3. Understand the names of various parts of the circle and the characteristics of the circle through specific operations.
(1) Fold the circle in half, open it, change the direction, fold it again, and then open it. . . . . . Repeat it several times.
Teacher's question: What did you find after folding it several times? There are many creases in the circle.
Look carefully, where do these creases always intersect in the circle? (center of circle)
The teacher pointed out: we call this point of the center of the circle the center of the circle.
Teacher's blackboard writing: the center of the circle
(2) Measure the distance from the center of the circle to any point on the circle with a ruler and have a look. What can you find?
(The distance from the center of the circle to any point on the circle is equal)
The teacher pointed out: we call the line segment connecting the center of the circle and any point on the circle radius, and the radius is generally expressed by letters.
The teacher asked: According to the concept of radius, what conditions should students have to think about a radius?
How many radii can a circle draw?
Are all radii equal in length?
Teacher's blackboard writing: The same circle has countless radii, all of which are equal in length.
(3) Students continue to observe: When the circle was folded in half just now, where did each crease pass through the circle? Where are the two ends of the circle?
The teacher pointed out: we call it a line segment passing through the center of the circle with both ends on the diameter of the circle. Diameter is generally indicated by letters. (The teacher draws a diameter in the circle and writes on the blackboard: Diameter)
Teacher's question: According to the concept of diameter, students think about it. What conditions should a diameter have?
How many diameters can a circle be drawn?
Measure several diameters in the same circle with a ruler and have a look. Are all diameters equal in length?
Teacher's blackboard writing: The same circle has countless diameters, and all the diameters are equal in length.
(4) Teacher's summary: Through the study just now, we know that the same circle has countless radii, all of which are radii.
Equal length; Countless diameters, all equal in length.
(5) Discussion: What is the relationship between the length of the inner diameter and the length of the radius of the same circle?
How to express this relationship in letters?
Conversely, in the same circle, the length of the radius is a fraction of the diameter.
Teacher's blackboard writing: In the same circle, the diameter is twice the radius.
(3) feedback exercises.
1. Mark the radius and diameter of each circle with a colored pen below.
2. Fill in the form.
(4) Drawing a circle.
According to the feature that the distance from the center of the circle to any point on the circle is equal, we can draw a circle with compasses.
1. Students learn by themselves
2. The teacher demonstrates drawing a circle.
3. The teacher summed it up on the blackboard: 1. Fixed radius; 2. fix the center of the circle; 3. Carry out a revolution.
The teacher stressed that when drawing a circle, the distance between the two feet of the compass should not change, and the foot with the needle tip should not move. When rotating, focus on the feet with needles.
4. Students practice
(5) Teachers ask questions
Why do students draw different circles? What determines the size of a circle? What determines the position of the circle?
Teacher writes on the blackboard: the radius determines the size of the circle, and the center of the circle determines the position of the circle.
(6) Thinking: In physical education class, the teacher wants to draw a big circle on the playground to play games. What if there are no compasses this big?
Third, the class summarizes.
What did we learn in this class? What did you get from this lesson?
Fourth, classroom exercises.
(1) judgment
1. When drawing a circle, the distance between two feet of the compass is the length of the radius. ()
2. The line segment with both ends on the circle is called the diameter. ()
The distance from the center of the circle to any point on the circle is equal. ()
A circle with a radius of 2 cm is larger than a circle with a diameter of 3 cm. ()
5. All circles have the same radius. ()
6. In the same circle, radius is diameter. ()
7. In the same circle, all diameters are equal in length. ()
8. Two radii can form a diameter. ()
Verb (abbreviation for verb) homework after class
(1) Draw a circle with a compass according to the following requirements.
1. Radius 2 cm.
2. Radius 2. 5 centimeters.
3. The diameter is 8 cm.
(2) How to measure the diameter of a circle without a center?
Sixth, blackboard design