\documentclass{article}
\usepackage{breqn}
\begin{document}
\begin{dmath}
\frac{\mathrm{d} \Pi}{\mathrm{d} u}=A E \int_{0}^{L} \frac{\mathrm{d} u}{\mathrm{~d} x} \frac{\mathrm{~d}(\delta u)}{\mathrm{~d} x}\mathrm{~d} x -\int_{0}^{L} q \delta u \mathrm{~d} x =0 \label{10}
\end{dmath}
\end{document}
但
我的代码使用 dmath,因为方程很大,我实际上在 IEEE 课堂上使用,所以帮助我装箱大方程式
答案1
给你:
\documentclass[svgnames]{article}
\usepackage{breqn}
\begin{document}
\begin{dmath}[frame, framesep={1em}]
\frac{\mathrm{d} \Pi}{\mathrm{d} u}=A E \int_{0}^{L} \frac{\mathrm{d} u}{\mathrm{~d} x} \frac{\mathrm{~d}(\delta u)}{\mathrm{~d} x}\mathrm{~d} x -\int_{0}^{L} q \delta u \mathrm{~d} x =0 \label{10}
\end{dmath}
\end{document}