\begin{frame}
  \frametitle{Properties of Formulas}

  \begin{block}{Equivalent formulas \mpause[1]{= true at the same time}}
    \mpause{
    \begin{tgather}
      \neg p \vee q \;\;\equiv\;\; p \to q
    \end{tgather}}\vspace{-1.5ex}
  \end{block}  
\end{frame}