Knowledge points:

1, acute angle is less than right angle, obtuse angle is greater than right angle. We can judge what kind of angle it is by the right angle on the triangular ruler.

2. A triangular ruler has (1) right angles and (2) acute angles. A square and a rectangle have four corners, all of which are right angles.

3. There are three angles on the red scarf, namely (1) obtuse angle and (2) acute angle.

Teaching objectives

1, through diagonal classification, know the right angle, acute angle and obtuse angle, know the relationship between them, judge the angle and draw the right angle.

2. Go through the process of dividing the angle, judging the angle, and finding the angle in connection with life. At the same time, learn to cooperate and communicate with others and learn to improve and perfect yourself.

3. Through the activities of teacher-student evaluation and experience exchange, we can build self-confidence and gain the joy of learning success. At the same time, I can feel that there is mathematics everywhere in my life and experience the fun of learning mathematics.