%%
%% The LaTeX Companion, 3ed
%%
%% Example 11-2-34 on page II-150 in "Equation numbering and tags".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3examargin}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{207.0pt}

%StartShownPreambleCommands
\usepackage{amsmath}
%StopShownPreambleCommands

\begin{document}
\begin{align}
  x^2+y^2 &= z^2 \label{eq:A}            \\
  x^3+y^3 &= z^3 \notag                  \\
  x^4+y^4 &= r^4 \tag{$*$}               \\
  x^5+y^5 &= r^5 \tag*{$*$}              \\
  x^6+y^6 &= r^6 \tag{\ref{eq:A}$'$}
\end{align}
\end{document}