Another important class of functions besides polynomials is exponential and logarithmic functions. Exponential and logarithmic functions are inverses of each other. An exponential function is a function of the form f (x) = a x , where a > 0, a≠1 , and x is any real number. The inverse of this function is a logarithmic function, f (x) = loga x . In the following sections, we'll review some characteristics of exponents and logarithms, and see how they apply to functions with exponents and logarithms. We'll also discuss the number e 2.718281828 and its special relevance to these types of functions. In the last section we'll take a look at some applications of these functions.