Error when setting a label in an alignat-environment which is embedded in a figure-environment

Question

I want to label equations in a alignat-environment which is embedded in a figure-environment and it won't compile. Example:

\documentclass[11pt,a4paper,twoside,openright]{book}

\usepackage{amsmath}

\begin{document}
 \begin{figure}
  \begin{alignat*}{2}
   a & = b  &  c & = d \\ \label{eq:1}
   e & = f  &  g & = h \\ \label{eq:2}
  \end{alignat*}
\caption{Equalities}
 \end{figure}

\end{document}

Error message:

! Package amsmath Error: Multiple \label's: label 'eq:1' will be lost.

See the amsmath package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.11   \end{alignat*}

Has anybody an idea how I can set the labels?

Answer 1

The \label commands work, if they are used in a numbered equation environment. Also they should put in the right lines:

\documentclass[11pt,a4paper,twoside,openright]{book}

\usepackage{amsmath}

\begin{document}
 \begin{figure}
  \begin{alignat}{2}
   a & = b  &  c & = d \label{eq:1}\\
   e & = f  &  g & = h \label{eq:2}
  \end{alignat}
\caption{Equalities}
 \end{figure}

\end{document}