Footnote in math mode: how to use symbols instead of numbers?

Question

In this and that post, it is explained how to put a footnote in math mode. The problem is that the number of footnotemark might be confused with exponents and viceversa: how can I use a symbol (say §, for example) instead?

Note I wish to use symbols only in math mode not in the rest of the text.

Answer 1

Don't footnote math. Never. However, if you don't want to listen to this advice, here's a way:

\documentclass{article}
\usepackage[papersize={8cm,6cm}]{geometry} % just to save space
\usepackage{bigfoot}

\DeclareNewFootnote[para]{math}[fnsymbol]
\MakeSortedPerPage{footnotemath}

\begin{document}

Some text with a footnote.\footnote{Some text in the footnote}
\[
a^n+b^n\ne c^n\,\footnotemarkmath
\]\footnotetextmath{I found a very smart proof of
this, but the footnote space doesn't contain it.}


\end{document}