# Footnote in math mode

How can I insert a footnote into math mode? I tried this (with required packages)

\usepackage{amsmath}
\usepackage{hyperref}
\usepackage{ccaption}


And i.e if I try

\begin{eqnarray}
foo && foo \text{\footnote{something}}\    foo && foo \mbox{\footnote{something else}}
\end{eqnarray}


the link to the footnote appears, but not in the footnote position and if I click it I'm redirected to the first page. If I am in text mode I don't have this problem. How can I do this? Thanks in advance!

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You shouldn't be using eqnarray, first of all, but rather align.

\begin{align}
a &= b && \text{something\footnotemark} \\
c &= d && \text{other}
\end{align}
\footnotetext{text of the footnote}


While \footnote works in equation, it doesn't in other alignment environments.

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your advice works with both (eqnarray and align) but from now on I'll use align –  Bruce_Warrior Jun 28 '11 at 15:10

According to Kopka and Daly, A Guide to LaTeX, p. 96--97, the \footnote command is not allowed in math mode, so you'll have to resort to using \footnotemark inside math environments and \footnotetext{<Some text>} in normal text mode.

Note that if, as in your example, more than one footnote is needed, you have to adjust the footnote counter by subtracting n-1 (n being the number of footnotes in math mode) before the first \footnotetext and using \stepcounter before all other occurences of \footnotetext.

\documentclass{article}

\begin{document}

\begin{eqnarray}
foo && foo \footnotemark\\
foo && foo \footnotemark
\end{eqnarray}

\footnotetext{something}
\stepcounter{footnote}
\footnotetext{something else}

\end{document}

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I do that but the firts footnotemark redirect me to first page and the second footnote works fine redirect me to the localization of the second footnote. Do you know why this happen to me? –  Bruce_Warrior Jun 28 '11 at 15:24

If you want to put footnotes in equation environment, just use \footnote in math mode:

$$foo\footnote{bar}$$


For eqnarray environment or some other complex environments, use:

\begin{eqnarray}
foo\footnotemark
\end{eqnarray}
\footnotetext{bar}


(Well, eqnarray is wicked, see \eqnarray vs \align)

However, it is not a good manner to use footnotes in math equations. The default marks could be considered as exponents. If it is really necessary, it is better to redefine \thefootnote to get a different mark style. For example:

% symbol sequence: * \dagger \ddagger \S \P ...
\renewcommand\thefootnote{\fnsymbol{footnote}}


or

% circled number: ①②③④⑤⑥⑦⑧⑨
\usepackage{pifont}
\renewcommand\thefootnote{\ding{\numexpr171+\value{footnote}}}

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