It is necessary to master the concept of angle defined by senior high school and the two units of angle, and understand the positive angle, negative angle and zero angle; A quadrant angle, an angle with the same terminal edge. The key to understanding these angles is that a ray rotates around the endpoint;

Trigonometric function is a special function with angle as independent variable. Therefore, we should use closely related function knowledge to master the knowledge in this chapter. For example, we should master the definition domain, range, maximum value, image, monotonicity, parity, periodicity and symmetry of sine, cosine and tangent functions.

You need to master a series of formulas you have learned before for trigonometric transformation.

This section contains a lot of content. Don't be afraid of it. Be patient and have more confidence. I hope it helps you.