高一课本定义了一一对应:设A、B是两个集合,f是从集合A到集合B的单值对应,如果对于集合A的不同元素,在集合B中有不同的象,而且B中的每一个元素都有原象,这个单值对应就叫做从A到B的一一对应。并在此基础上定义了反函数。因此,欲求已知函数y=f(x)的反函数,必须事先判定函数y=f(x)的定义域与值域之间的单值对应y=f(x)是不是一一对应。若是一一对应,则其反函数存在,且可根据书上的方法求出;若不是一一对应,则其反函数不存在,须对定义域给予适当的限制,使之与值域之间构成一一对应,从而 A high school textbook defines a one-to-one correspondence: Let A and B be two sets, f be a single value correspondence from set A to set B, if there are different images in set B for different elements of set A, and B Each element in it has a primary image. This single value corresponds to a one-to-one correspondence from A to B. Based on this, the inverse function is defined. Therefore, in order to find the inverse function of the known function y=f(x), it must be determined in advance whether the single value correspondence between the domain of the function y=f(x) and the value domain corresponds to whether y=f(x) is a one-to-one correspondence. If there is a one-to-one correspondence, its inverse function exists, and can be found according to the method of the book; if it is not a one-to-one correspondence, its inverse function does not exist, and the domain should be given appropriate restrictions, so that it is between the value domain Constitute a one-to-one correspondence