A rational function is a function that contains a rational expression. Any function that can be written as the quotient of two polynomial functions $p(x)$ and $q(x)$ is a rational function. For any values of $x$ where $q(x)=0,$ the rational function is undefined. These values are excluded from the domain of the function. One example of a rational function is the reciprocal function. This function has two asymptotes, the $x\text{-}$axis and the $y\text{-}$axis. The applet shows the graph of the reciprocal function and some other rational functions.