First of all, setting, setting must pay attention to the critical point, whether there is a critical point.

Secondly, the function, the solution of the domain in the function is error-prone. It is necessary to understand that the brackets are unchanged, the domain is the range of X, the function must be marked with the domain, and the domain must be looked at when solving the domain and monotonous interval. Also, when seeking parity, we must look at whether the domain is symmetrical about the origin.

Compulsory 4: Compulsory 4 is mainly trigonometric function. Trigonometric function must see clearly which trigonometric function it is and remember the relationship of each trigonometric function, and remember the domain scope of trigonometric function. The range of sine and cosine is negative one to one, which has always been a problem here. Tangent domain has a range.