\begin{frame}[fragile]
  \frametitle{Examples}
  
  \begin{exampleblock}{Example: $p \vee (q \wedge r) \;\;\vdash\;\; p \vee q$}
  \medskip{\small
  \begin{verbatim}
Theorem ex4 : (A \/ (B /\ C)) -> (A \/ B).\end{verbatim}
  \pause
  \begin{verbatim}
  Proof.
  imp_i H.
  f_dis_e H HA HBC.
  f_dis_i1 HA.
  dis_i2.
  f_con_e1 HBC.
  Qed.\end{verbatim}
  \smallskip}
  \end{exampleblock}  
\end{frame}