标记方程式

Question

我想给一个方程式起个名字，叫“ن的逆”

我写作时使用多语

    \documentclass[12pt,a4paper,openany]{book}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\usepackage{titlesec}
\usepackage{titletoc}
\usepackage{etoolbox}
\usepackage{multicol}
\usepackage{titleps}
%%%%%%%%%%%%%%%%%%%%%%%%%%
\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{compat=1.15}
\usepackage{mathrsfs}
\usepackage{amsmath,amssymb,amsthm}
\usepackage{geometry}
%%%%%%%%%%%%%%%%%%%
\usetikzlibrary{arrows}
\usepgfplotslibrary{fillbetween}
\usetikzlibrary{patterns}
\usetikzlibrary{patterns,shapes.geometric}
%%%%%%%%%%%%%%%%%%%
\usepackage{fancyhdr}
\pagestyle{fancy}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%


\usepackage{polyglossia}
\setmainlanguage[numerals=maghrib]{arabic}
\setotherlanguage{english}
\newfontfamily\arabicfont[Script=Arabic,Scale=1.1,AutoFakeSlant=-0.03]{Amiri}
\setsansfont[Script=Arabic,Scale=1.1]{Amiri}




\begin{document}

\begin{equation}\label{n}{\tag{\reflectbox{ن}}}
a=b
\end{equation}
\end{document}

它在 end{equation} 处给出许多错误

第一个是

undefined control sequence.
\bidiGscale@box...\fi\leavevmode\def\Gscale@y{#2}\se...\end{equation}

但是如果删除 \tag 没有错误，请问如何给方程式赋予这个名称？

谢谢