The related contents and exercises of teaching content are on page 42 of the textbook.
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Teaching objectives
1. Make students know the reading range of 1 right angle =90 degrees, 1 right angle = 180 degrees, 1 rounded corner =360 degrees, and the reading range of obtuse angle and acute angle, and distinguish these angles according to their degrees to understand the relationship between them.
2. Dynamically experience the formation process of various angles and the classification process of angles, and experience the cognitive process from intuition to abstraction and the classification thought in mathematics.
3. Enable students to accumulate rich experience in basic activities of mathematics in the learning process.
Teaching focuses on the understanding of straight corners and rounded corners, and different angles can be distinguished according to their degrees.
The teaching difficulty is to understand the dynamic formation process of boxers and rounded corners and the relationship between the five angles.
Demonstration of teaching methods
Learn to observe, think and operate.
Teaching aid preparation courseware, protractor, triangular ruler, activity angle.
teaching process
First, check the import.
1. Dialogue: Last time we learned the definition of angle. What is an angle? I also learned to measure angles with a protractor. Please take out your triangular ruler and measure the maximum angle.
2. After students independently measure the angle, name the method and report the degree.
Second, explore new knowledge.
(A) dynamic understanding of right angles, acute angles and obtuse angles
1. What is a 90-degree angle? So 1 right angle = 90 (blackboard writing)
2. Can we still understand this 90 right angle?
Courseware demonstration: A right angle is the angle formed by a ray rotating 90 around its endpoint.
3. Besides right angles, what other angles have we learned? (acute angle and obtuse angle)
4. What is an acute angle? Of course, an acute angle can also be regarded as the rotation of light around its endpoint by a certain angle, such as 30. Who can say how it was formed? So what is the degree range of acute angle?
5. What is an obtuse angle? How is the obtuse angle of 135 formed? What is the degree of obtuse angle?
Default: Students will say an angle greater than 90.
The teacher questioned whether anything greater than 90 is an obtuse angle. Let's continue to understand the angle.
(2) Know the Boxer Rebellion
1. Please use the movable angle in your hand to rotate to the semicircle position and name the blackboard for demonstration. Can you point out the vertex and sides of this angle?
What did you find? Name the students to answer.
2. courseware demonstration, teacher: after a ray rotates around its endpoint for half a week, the angle formed is no longer obtuse. Let's call it a straight angle. (Unified reading definition)
3. Question: What is the degree of 1 flat angle? Can you tell me how you know?
Preset: raw 1: measure with protractor180;
Health 2: Two right angles add up to a right angle, so it is 180.
Blackboard: 1 boxer = 180
4. Is it rigorous to say that the obtuse angle is greater than 90? Why? So what is the degree range of obtuse angle?
5. Thinking: Is a right angle a straight line?
Tell the reasons and lead the students to the conclusion that a right angle has a vertex and two sides, which is an angle rather than a straight line.
(3) Understanding fillet
1. Dialogue: We just met a boxer. If you continue to rotate the movable angle, what new angle can you form?
2. Take out the movable angle and rotate it to the position of one week. This figure is also a corner, called a fillet. Can you point out the vertex and sides of this angle? What's wrong with these two sides?
3. Who can try to give the definition of fillet? Courseware demonstration, teacher: a ray rotates around its endpoint once, and the angle formed is called fillet.
4. Question: What is the temperature of the fillet? what do you think?
Default: healthy 1: half a week is 180 degrees, and one week is two 180 degrees, which is 360 degrees.
Health 2: Four right angles add up to a rounded corner, so it is 360.
Blackboard: 1 fillet = 360.
5. Thinking: Is the fillet a ray?
Tell the reason and guide the students to draw the conclusion that the fillet has a vertex and two sides overlap, which is an angle rather than a ray.
(4) Classification of angles
Through the study just now, we got to know three old friends, namely right angle, acute angle and obtuse angle, and two new friends-straight angle and rounded angle. What is the relationship between these five angles? Let's work together at the same table and answer the following three questions:
(1) According to the size of the angle, what types can the angle be divided into?
(2) How should they be arranged in descending order?
(3) What is the relationship between rounded corners, right angles and right angles?
Report by name.
1, angles can be divided into acute angle, right angle, obtuse angle, right angle and rounded angle.
2. acute angle