How can I add a dot under Chinese characters and paragraph?

Question

I'm trying to practice TeX by typing my algebra textbook, but now I have a problem when adding dot under Chinese characters. The picture shows where I encountered this problem. I tried \dot in math mode and \d in text mode, but they don't work.

My code goes like this:

\documentclass{ctexbook}
\usepackage{amsmath}
\usepackage{indentfirst} 
\setlength{\parindent}{2em}
\setcounter{page}{98}
\begin{document}
\[
\boldsymbol{\gamma}=\boldsymbol{\gamma}_0+\boldsymbol{\eta},
\]
\dot{其}中 $\boldsymbol{\eta}$ 是导出组 (1) 的一个解. 因此, 对于方程组 (9) 的任一个特解 $\gamma_0$, 当 $\boldsymbol{\eta}$ 取遍它的导 出组的全部解时, (10) 就给出 (9) 的全部解.

I got an error:

Package amsmath Error: \dot allowed only in math mode. \dot{其}

I need amsmath to show my math formula, how could I solve this problem?

Answer 1

If you're using xelatex, you can use \CJKunderdot of the xeCJKfntef package (documented with xeCJK).

\documentclass{ctexbook}
\usepackage{amsmath}
\usepackage{indentfirst}
\usepackage{xeCJKfntef}
\usepackage{unicode-math}
\setlength{\parindent}{2em}
\setcounter{page}{98}
\begin{document}
\[
\symbf{\gamma}=\symbf{\gamma}_0+\symbf{\eta},
\]
\CJKunderdot{其中 $\symbf{\eta}$ 是导出组 (1) 的一个解. 因此, 对于方程组 (9) 的任一个特解 $\gamma_0$, 当 $\symbf{\eta}$ 取遍它的导 出组的全部解时, (10) 就给出 (9) 的全部解.}
\end{document}

Note that I also loaded unicode-math and changed \boldsymbol to \symbf (I think this is recommended practice with unicode engines).