行距太小。如何调整?
\begin{equation}\tag{12}
\left\{
\begin{array}{ll}
U_{1}(x) = \sum_{|n| \leq N} A_{n}e^{i\alpha_{n}x} + \sum^{2}_{l
= 1}a_{l} \frac{x^{l}}{l!} \\
U^{'}_{1}(x) = \sum_{|n| \leq N}
A_{n}i\alpha_{n}e^{i\alpha_{n}x} + \sum^{2}_{l = 1}a_{l}
\frac{x^{l - 1}}{(l - 1)!}
\end{array}
\right. \texttt{where $\alpha_{n}$ = 2n$\pi{}$}
\end{equation}
答案1
两个解决方案的代码更简单:一个dcases
来自 的环境(displaystyle cases)mathtools
,另一个来自empheq
环境。不加载amsmath
:empheq
加载mathtools
,这会加载它。
\documentclass{article}
\usepackage{empheq}
\begin{document}
\begin{equation}
\begin{dcases}
U_1(x) = \sum_{|n| \leq N}A_n e^{i\alpha_n x} + \sum^2_{l=1}a_l \frac{x^l}{l!} \\
U'_1(x) = \sum_{|n| \leq N}A_n i\alpha_n e^{i\alpha_n x} + \sum^2_{l=1}a_l \frac{x^{l - 1}}{(l - 1)!}
\end{dcases}
\quad\text{where}\quad \alpha_n = 2n\pi
\end{equation}
\begin{empheq}[left=\empheqlbrace]{equation}
\begin{aligned}
U_1(x) & = \sum_{|n| \leq N}A_n e^{i\alpha_n x} + \sum^2_{l=1}a_l \frac{x^l}{l!} \\%[2\jot]
U'_1(x) & = \sum_{|n| \leq N}A_n i\alpha_n e^{i\alpha_n x} + \sum^2_{l=1}a_l \frac{x^{l - 1}}{(l - 1)!}
\end{aligned}
\quad \text{where}\quad \alpha_n = 2n\pi
\end{empheq}
\end{document}
答案2
这里有一些选项,包括添加\displaystyle
垂直拉伸案例:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\left\{
\begin{array}{ l l }
U_1(x) = \sum_{|n| \leq N}A_n e^{i\alpha_n x} + \sum^2_{l=1}a_l \frac{x^l}{l!} \\
U'_1(x) = \sum_{|n| \leq N}A_n i\alpha_n e^{i\alpha_n x} + \sum^2_{l=1}a_l \frac{x^{l - 1}}{(l - 1)!}
\end{array}
\right. \text{where $\alpha_n = 2n\pi$}
\end{equation}
\begin{equation}
\left\{\setlength{\arraycolsep}{0pt}
\begin{array}{ r l @{\quad} l }
U_1(x) &{}= \sum_{|n| \leq N}A_n e^{i\alpha_n x} + \sum^2_{l=1}a_l \frac{x^l}{l!} \\[2\jot]
U'_1(x) &{}= \sum_{|n| \leq N}A_n i\alpha_n e^{i\alpha_n x} + \sum^2_{l=1}a_l \frac{x^{l - 1}}{(l - 1)!}
\end{array}
\right. \text{where $\alpha_n = 2n\pi$}
\end{equation}
\begin{equation}
\left\{\setlength{\arraycolsep}{0pt}
\begin{array}{ r l @{\quad} l }
U_1(x) &{}= \displaystyle\sum_{|n| \leq N}A_n e^{i\alpha_n x} + \sum^2_{l=1}a_l \frac{x^l}{l!} \\[\jot]
U'_1(x) &{}= \displaystyle\sum_{|n| \leq N}A_n i\alpha_n e^{i\alpha_n x} + \sum^2_{l=1}a_l \frac{x^{l - 1}}{(l - 1)!}
\end{array}
\right. \text{where $\alpha_n = 2n\pi$}
\end{equation}
\end{document}
最后,由于您使用array
设置案例,因此您可以使用以下方法调整垂直间距表格中的列和行填充。