First, knowledge and skills:

1. Understand the meaning of acute trigonometric function, and understand that the ratio of the opposite side to the hypotenuse of an acute angle in a right triangle is the sine of this acute angle, and its sine value is constant when the acute angle is fixed;

2. According to the known side length of the right triangle, the sine value of the acute angle can be obtained. 2. Process method:

Through the exploration of the definition of trigonometric function of acute angle, it is gradually found that the ratio of the opposite side to the hypotenuse of an acute angle is constant, and the mathematical connotation revealed by this law is considered.

Third, emotional attitude:

Make students experience the exploration and discovery in mathematical activities, cultivate students' deductive reasoning ability from special to general, and learn to think, discover, summarize and verify with mathematical thinking mode.

2. Teaching emphases/difficulties

Teaching emphasis: If you understand the concept of sine correctly, you will get the sine value of acute angle according to the side length of right triangle. Difficulties in teaching: Understand that in a right triangle, for any acute angle, the ratio of the opposite side to the hypotenuse is a constant value.

3. Teaching tools. label