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答案1
对于练习册,我发现它很有用,但我会根据以下内容使用不同的对齐方式alignedat
:
\documentclass{article}
\usepackage{amsmath}
\newcommand\diff{\mathop{}\!d}
\begin{document}
\begin{equation*}
\int x \log x \diff x =
\left[
\begin{alignedat}{2}
u &= \log x \quad & \diff v &= x\diff x \\
\diff u &= \frac{1}{x}\diff x \quad & v &= \frac{x^2}{2}
\end{alignedat}\,
\right]
=
\frac{x^2}{2}\log x - \int \frac{x^2}{2}\frac{1}{x}\diff x
\end{equation*}
\end{document}
上面那条线表示你开始的是什么,下面那条线表示你得到的是什么。
另一种方法是按列而不是按行:
\documentclass{article}
\usepackage{amsmath}
\newcommand\diff{\mathop{}\!d}
\begin{document}
\begin{equation*}
\int x \log x \diff x =
\left[
\begin{alignedat}{2}
u &= \log x \quad & \diff u &= \frac{1}{x}\diff x\\
\diff v &= x\diff x \quad & v &= \frac{x^2}{2}
\end{alignedat}\,
\right]
=
\frac{x^2}{2}\log x - \int \frac{x^2}{2}\frac{1}{x}\diff x
\end{equation*}
\end{document}