\documentclass[12pt]{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{amssymb}
\usepackage{amsfonts}
\usepackage{anyfontsize}
\usepackage{bm}
\pagestyle{empty}
<%= preamble %>

\usepackage[active<%= tightpage %>]{preview}

\begin{document}
\begin{preview}
\fontsize{<%= fontsize %>}{<%= baselineskip %>}\selectfont <%= math %>
\end{preview}
\end{document}