Mathematically, sin stands for sine function and is one of trigonometric functions. In the unit circle, when the distance from the radian value corresponding to an angle to the X axis is equal to the sin value, the sin value of this angle can be calculated. Sinusoidal functions are widely used in many disciplines, such as physics, engineering and astronomy.

Sinusoidal function has the following characteristics: it is a periodic function with a period of 2π; Its amplitude is1; Its image is the largest when x=π/2 and the smallest when x=3π/2. In addition, since the sin function can be regarded as the value of the Y-axis coordinate in the unit circle, its value range is [- 1, 1].

For example, a triangle with any angle, we can use the sin function to calculate the angle. If you know one side of the angle and the opposite side of the angle, you can use sine function to calculate the angle. Use sin A = a/h to calculate the value of angle a, where h is the length of the hypotenuse and a is the length of the opposite side of angle a. This is a useful use of the sin function in the example.