\begin{frame} \frametitle{Example from a Previous Exam} \begin{exampleblock}{} Show that \quad$\vdash\; \neg q \vee (p \to q)$\quad: \smallskip \begin{tikzpicture} \naturaldeduction{ \mpause[1]{ \proofstep{$q \vee \neg q$}{LEM}; } \mpause{ \proofbox{ \mpause{ \proofstep{$q$}{assumption}; } \mpause{ \proofbox{ \mpause{ \proofstep{$p$}{assumption}; } \mpause{ \proofstep{$q$}{copy 2}; } } } \mpause{ \proofstep{$p \to q$}{$\to_i$ 3--4}; } \mpause{ \proofstep{$\neg q \vee (p \to q)$}{$\vee_{i_2}$ 5}; } } } \mpause{ \proofbox{ \mpause{ \proofstep{$\neg q$}{assumption}; } \mpause{ \proofstep{$\neg q \vee (p\to q)$}{$\vee_{i_1}$ 6}; } } } \mpause{ \proofstep{$\neg q \vee (p\to q)$}{$\vee_{e}$ 1,\;2--6,\;7--8}; } } \end{tikzpicture} \end{exampleblock} \end{frame}