latex 中心化 编号方程

Question

我有以下代码。为什么我的方程式没有居中？我该如何让它们居中？

\documentclass[10pt,a4paper,fleqn]{article}
\usepackage{amsmath, amsfonts, amsthm, amssymb}
\usepackage[a4paper,margin=1in]{geometry}
\usepackage{anysize,graphicx,cite,fancyhdr}
\usepackage{mathptmx}
\usepackage{caption}
\usepackage{authblk}

\numberwithin{equation}{section}

\usepackage[T1]{fontenc}         % Not always necessary, but recommended.
% End of standard header.  What follows pertains to the problem at hand.

\marginsize{2.0cm}{2.0cm}{2.0cm}{2.0cm}
\pagestyle{fancy}
\lhead{}
\rhead{}
\chead{}
\cfoot{}
\renewcommand{\headrulewidth}{0pt}


\title{\Large \bf title}
\date{}
\author[1,*]{{author 1}}
\author[1]{author 2}
\affil[1]{\normalsize affiliation
\\ *Email: blank}
\begin{document}

\maketitle
\thispagestyle{fancy}

\noindent\textit{Keywords:Title}

\bigskip
\noindent\textbf{Abstract}\\

text text text

\section{Introduction}


\begin{align}
\ddot{\underline{\mathbf{r}}} &= \frac{d{^2}\underline{\mathbf{r}}}{dt^2}\\
                              &= 0
\end{align} 

%Equations with no numbering in specific line by using \nonumber
\begin{align}
\ddot{\underline{\mathbf{r}}} &= \frac{d{^2}\underline{\mathbf{r}}}{dt^2}\nonumber\\
                              &= 0
\end{align}



$$A(\rho,T) = A_0(\rho)+A_i(\rho,T)+A_e(\rho,T)$$


\section{Methodology}

\section{Results and Discussion}

\section{Conclusion}

\section{Acknowledgments}


\bibliographystyle{IEEEtran}
\bibliography{library}



\end{document}

Answer 1

fleqn加载时删除该选项\documentclass。