Combination refers to combining two functions into a new function. . My understanding is just so-so. . )

The following is the definition of composite function:

Let the domain of y=f(u) be Du, the domain of value be Mu, the domain of function u=g(x) be Dx, and the domain of value be Mx, then any X in Dx passes through U; There is a unique fixed value of y corresponding to it, so a functional relationship between variables X and Y is formed by variable U, which is denoted as: y=f[g(x)], and this function is called a composite function, where X is called an independent variable, U is an intermediate variable and Y is a dependent variable (i.e. a function).

You can download the "composite function" again to get a more comprehensive understanding. .