init.tex

\newenvironment{absolutelynopagebreak}
{\par\nobreak\vfil\penalty0\vfilneg
 \vtop\bgroup}
{\par\xdef\tpd{\the\prevdepth}\egroup
 \prevdepth=\tpd}

\newcommand{\uitwerking}[1]{
	\begin{tabular}{|ll}
    	#1 &
	\end{tabular}
}

\newcommand{\definitie}[2]{
	\begin{absolutelynopagebreak}
		\textbf{Def:} #1\\*
		\uitwerking{#2}\\*
	\end{absolutelynopagebreak}
}

\newcommand{\als}[1]{
    \textbf{Als:} #1
}

\newcommand{\feit}[1]{
    \textbf{Feit:} #1\\
}

\newcommand{\voorbeeld}[1]{
		\textbf{Voorbeeld:}\\
		\uitwerking{#1}\\
}
\newcommand{\gevolg}[1]{
		\textbf{Gevolg:}\\
		\uitwerking{#1}\\
}

\newcommand{\bewijs}[1]{
	\begin{absolutelynopagebreak}
		\textbf{Bewijs:}\\
		\uitwerking{#1}\qed
	\end{absolutelynopagebreak}
}

\newcommand{\stelling}[1]{
	\begin{absolutelynopagebreak}
    \textbf{Stelling:} #1\\
	\end{absolutelynopagebreak}
}

\newcommand{\lemma}[1]{
    \textbf{Lemma:} #1\\
}

\newcommand{\propositie}[1]{
    \textbf{Propositie:} #1\\
}

\newcommand{\N}[0]{
   \mathbb{N}
}
\newcommand{\Z}[0]{
   \mathbb{Z}
}
\newcommand{\Q}[0]{
   \mathbb{Q}
}
\newcommand{\R}[0]{
   \mathbb{R}
}
\newcommand{\C}[0]{
   \mathbb{C}
}