### 这个是《TeXLive下mtpro2字体安装与使用》，我删减了一些内容，我想问一下如何使这篇文档的正文和数学环境中的数字字体为times ####使用XeLaTeX编译 ```tex \documentclass{ctexart} \usepackage{etex} \usepackage{geometry} \usepackage{times} \usepackage[scaled=0.92]{helvet} \usepackage[lite,subscriptcorrection,slantedGreek,nofontinfo]{mtpro2} \renewcommand{\rmdefault}{ptm} \usepackage{amsmath} \usepackage[thmmarks,amsmath]{ntheorem} \theoremstyle{nonumberplain} \theoremheaderfont{\bfseries} \theorembodyfont{\normalfont} \everymath{\displaystyle} \newtheorem{example}{例题} \newtheorem{proof}{证明} \newtheorem{solution}{解} \usepackage{graphicx} \geometry{left=3cm,right=2.5cm,top=2.5cm,bottom=2.5cm} \usepackage{hyperref} \usepackage{tikz} \usetikzlibrary{shadings,arrows.meta,matrix,positioning,shapes.geometric,calc,fit,decorations.pathmorphing} \usepackage[os=win,hyperrefcolorlinks]{menukeys} \renewmenumacro{\menu}[>]{angularmenus} \renewmenumacro{\keys}[+]{shadowedroundedkeys} \title{TeXLive下mtpro2字体安装与使用} \author{八一} \date{\today} \begin{document} \maketitle \begin{center} 微信公众号：八一考研数学竞赛 \end{center} \begin{example}[南开大学2019年数学分析第4题] 设函数$f\left(x,y,z\right)=2x^2+2xy+2y^2-3z^2\textbf{，}\overline{l}=\left(\frac{\sqrt{2}}{2},-\frac{\sqrt{2}}{2},0\right)$，动点$P$在曲面$x^2+2y^2+3z^2=1$，求方向导数$\left.\frac{\partial f}{\partial l}\right|_{\left(P\right)}$的最大值. \end{example} \begin{solution} 由题设可知$f_{x}=4 x+2 y, f_{y}=2 x+4 y, f_{z}=-6 z$以及方向$\overline{l}$余弦 \[ \cos \alpha=\frac{\sqrt{2}}{2} ,\cos \beta=-\frac{\sqrt{2}}{2} , \cos \gamma=0 \] 即$\left.\frac{\partial f}{\partial l}\right|_{\left(P\right)}=\sqrt{2}\left(x-y\right)$.利用拉格朗日数乘法，令 $L(x, y, z, \lambda)=\sqrt{2}\left(x-y\right)+\lambda\left(x^{2}+2 y^{2}+3 z^{2}-1\right)$，得 \[ \left\{\begin{array}{l} L_x=\sqrt{2}+2\lambda x=0\\ L_y=\sqrt{2}-2\lambda x=0\\ L_z=6\lambda z=0\\ L_{\lambda}=x^2+2y^2+3z^2-1=0\\ \end{array}\right.\Rightarrow\lambda =\pm 1,x=\mp\frac{\sqrt{2}}{2},y=\pm\frac{\sqrt{2}}{2} \] 因此方向导数$\left.\frac{\partial f}{\partial l}\right|_{\left(P\right)}$的最大值2. \end{solution} \end{document} ```