\begin{frame}[t] \begin{block}{} \begin{center} $\begin{array}{llcl} (1)&e\cdot x&\to&x\\ (2)&I(x)\cdot x&\to&e\\ (3)&(x\cdot y)\cdot z &\to& x\cdot (y\cdot z) \end{array}$ \end{center} \end{block} \bigskip\pause Critical pairs: \begin{itemize} \onslide<3-> \item between (1) and (3): $\langle y\cdot z,\; e\cdot (y\cdot z)\rangle$ \hfill\onslide<4->{\alert<4>{convergent\quad\quad}} \onslide<5-> \item between (2) and (3): $\langle e\cdot z,\; I(x)\cdot (x\cdot z)\rangle$ \hfill\onslide<6->{\alert<6>{not convergent\quad\quad}} \end{itemize} \onslide<7-> \begin{center} \begin{tikzpicture}[very thick,->] \node (t) {$(I(x)\cdot x)\cdot z$}; \node (l) [below left=of t] {$e\cdot z$}; \node (r) [below right=of t] {$I(x)\cdot(x\cdot z)$}; \draw (t) -- (l) node [midway,above left] {$2$}; \draw (t) -- (r) node [midway,above right] {$3$}; \onslide<8->{\node (l') [node distance=7mm,below=of l] {$z$};} \onslide<8->{\draw (l) -- (l') node [midway,left] {$1$};} \onslide<9->{\draw [dashed] (r) -- (l') node [midway,above right] {$4$};} \end{tikzpicture} \end{center} \vspace{-1ex} \onslide<9-> Add a rule: \begin{block}{} (4)\hspace{2em} $I(x)\cdot (x\cdot z)\to z$ \end{block} \end{frame}