\begin{frame} \frametitle{Derivative as a Function} \begin{block}{} A function $f$ is \emph{differentiable at $a$} if $f'(a)$ exists. \end{block} \pause\smallskip \begin{block}{} A function $f$ is \emph{differentiable on an open interval $(a,b)$} if it is differentiable at every number of the interval. \end{block} \pause Note that the interval $(a,b)$ may be $(-\infty,b)$, $(a,\infty)$ or $(-\infty,\infty)$.\\ % \pause\medskip \end{frame}