\begin{frame}
  \frametitle{Maximum and Minimum Values}

    \begin{center}\vspace{-2ex}
    \scalebox{.85}{
    \begin{tikzpicture}[default,baseline=1cm]
      \def\diay{}
      \diagram{-1}{5}{-.5}{3.5}{1}
      \diagramannotatez
      \def\xa{.5}
      \def\xb{1}
      \def\xc{2}
      \def\xd{2.5}
      \def\xe{3.5}
      \def\xf{4.5}
      \begin{scope}[cgreen,ultra thick]
         \draw (\xa,2) to[out=-50,in=90] (\xb,1) to[out=90,in=180] (\xc,3) to[out=0,in=115] (\xd,2.5)  to[out=-65,in=180,looseness=.5] (\xe,.5) to[out=0,in=190,looseness=.5] (\xf,3.5);
      \end{scope}
      \begin{scope}[gray]
        \draw (\xa,2) -- node[black,at end,below] {$a$} (\xa,-.2);
        \draw (\xb,1) -- node[black,at end,below] {$b$} (\xb,-.2);
        \draw (\xc,3) -- node[black,at end,below] {$c$} (\xc,-.2);
        \draw (\xd,2.5) -- node[black,at end,below] {$d$} (\xd,-.2);
        \draw (\xe,.5) -- node[black,at end,below] {$e$} (\xe,-.2);
        \draw (\xf,3.5) -- node[black,at end,below] {$f$} (\xf,-.2);
      \end{scope}
    \end{tikzpicture}
    }
    \end{center}
    Which of the points are global/local maxima/minima?
    \begin{itemize}
    \pause
      \item [$a$] \ \pause nothing
    \pause
      \item [$b$] \ \pause local minimum
    \pause
      \item [$c$] \ \pause local maximum
    \pause
      \item [$d$] \ \pause nothing
    \pause
      \item [$e$] \ \pause local and global (absolute) minimum
    \pause
      \item [$f$] \ \pause global (absolute) maximum, but not a local maximum
    \end{itemize}
\end{frame}