Mac:TexStudio 标准数学公式

\documentclass[conference, 12pt]{IEEEtran}

\usepackage{xeCJK}
\usepackage{fontspec}
\setmainfont{Times New Roman}
\usepackage{cite}
\usepackage{amsmath} %提供\begin{equation}
\usepackage{amssymb} %提供\substack

\begin{document}

\title{题目}
\author{\IEEEauthorblockN{作者}\IEEEauthorblockA{学号\\学院\\大学}}
\maketitle

\begin{abstract}
	摘要
\end{abstract}

\section{Introduction}
引言\cite{sample1}

\section{Methodologies}
\begin{equation}
	f(x) = \sum_{i=1}^{n} {x_i}
\end{equation}

\begin{equation}
	f(x) = x_1 + x_2 + x_3 + ...... + x_n
\end{equation}

\begin{equation}
	f(x) = \int_{i=1}^{n} {x_i}
\end{equation}

\begin{equation}
	X=
	\begin{cases}
	5, \text{if X is divisible by 5}
	\\
	10, \text{if X is divisible by 10}
	\\
	-1, \text{otherwise}
	\end{cases}
\end{equation}

\begin{equation}
	X = 
	\frac{\substack{\sum{X_i}}}
	{\substack{\sum{X_j}}}
\end{equation}

\begin{equation}
	X \leqslant y %x<=y
\end{equation}

\begin{equation}
	X \geqslant y %x>=y
\end{equation}

\bibliographystyle{IEEEtran}
\bibliography{ieetutorial}
\end{document}