\import{set.tex}
\import{relation.tex}

\begin{definition}\label{phase5_apply}
    $\apply{f}{x} = \unions{\img{f}{\{x\}}}$.
\end{definition}

\begin{proposition}\label{phase5_application_surface}
    Then $f(x) = y$.
\end{proposition}

\begin{proposition}\label{phase5_application_explicit}
    Then $\apply{f}{x} = y$.
\end{proposition}