The discussion of functions is nothing more than: definition range, range, monotonicity, parity and periodicity in trigonometric functions, and understanding the definitions and characteristics of various functions, such as exponential functions. First, y=a? The range of x and a determines the monotonicity of the function, and it has no parity as far as images are concerned. To learn functions well, we must first be familiar with concepts, how we define various functions and what their characteristics are. Textbooks are very useful, although simple, but the things summed up are very practical, and it is most important to look at textbooks ~