这是我想要用 LaTex 写的方程式:
我读过了这些建议,但对于拆分和多行命令,它说它们未定义(对于多行也是如此,但这对我来说并不适合)。还有其他断行的可能性吗?
答案1
包empheq
(加载mathtools
和amsmath
)允许将任何内容放在一组方程的左侧或右侧。因此,这是另一个解决方案,具有环境gather*
:
\documentclass[12pt,a4paper,bothsides]{article}
\usepackage[utf8]{inputenc}
\usepackage[showframe, nomarginpar]{geometry}
\usepackage[overload]{empheq}
\begin{document}
\begin{gather*}[left ={ V_{i,j} = \empheqlbrace}, right = \empheqrbrace ]
a + b = c + d \\
∫_0¹ x² \ \mathrm{d}x = \dfrac{1}{3}\\
\nabla u = 0
\end{gather*}
\end{document}
答案2
由于您已经在评论中指出分号是为了表示“如果...”的关系,我建议您将材料显示在两个单独的列中,并在第二列的开头;
用 替换。if
此外,由于相同的、相当复杂的表达式在花括号之间出现了五次,我建议您事先定义它并给它一个简写,比如说。\widehat{W}
(您显然可以自由地想出一个更合适的简写符号!)然后使用环境array
或dcases
环境来陈述V_{ij}
是什么,\widehat{W}
或者您最终选择的任何符号——让它出现五次。
这种设置——首先,定义复杂的表达式;其次,在陈述是什么时反复使用它V_{ij}
——应该让读者更容易地关注论点的结构。
\documentclass{article}
\usepackage{mathtools}
\DeclarePairedDelimiter{\abs}{\lvert}{\rvert}
\begin{document}
Let $\displaystyle\widehat{W}\equiv W_{j}\ln\biggl( 1 +
\frac{G_{i,j} \abs{h_{i,j}}^2 P_{i,j}} {\sigma_{i,j}^2} \biggr)$. Then
\[
\renewcommand\arraystretch{1.5} % more space between lines to mimic display style
V_{i,j} =
\left\{\begin{array}{ll}
(Q_{1}D_{i}^{d} + Q_{2}D_{i}^{o}) \widehat{W}
& \text{if } D_{i}^{d} + D_{i}^{o} \leq \widehat{W}\\
Q_{1}D_{i}^{d} \widehat{W}
& \text{if } D_{i}^{d} \leq \widehat{W} < D_{i}^{d} + D_{i}^{o}\\
0
& \text{if } \widehat{W} < D_{i}^{d}
\end{array}\right\}
\]
Or, using the \texttt{dcases} environment:
\[
V_{i,j} =
\begin{dcases} % dcases environment is provided by the mathtools package
(Q_{1}D_{i}^{d} + Q_{2}D_{i}^{o}) \widehat{W}
& \text{if } D_{i}^{d} + D_{i}^{o} \leq \widehat{W}\\
Q_{1}D_{i}^{d} \widehat{W}
& \text{if } D_{i}^{d} \leq \widehat{W} < D_{i}^{d} + D_{i}^{o}\\
0
& \text{if } \widehat{W} < D_{i}^{d}
\end{dcases}
\]
\end{document}
答案3
另一个解决方案:
\documentclass{article}
\usepackage{geometry}
\usepackage{mathtools}
\DeclarePairedDelimiter{\abs}{\lvert}{\rvert}
\begin{document}
\begin{equation*}
V_{i,j} =
\begin{Bmatrix}
\displaystyle (Q_{1}D_{i}^{d} + Q_{2}D_{i}^{o})W_{j}\ln{\mkern -7mu}\left(1 + \frac{G_{i,j}\abs{h_{i,j}}^{2}P_{i,j}}{\sigma_{i,j}^{2}}\right){\mkern -5mu}; D_{i}^{d} + D_{i}^{o} \leq W_{j}\ln{\mkern -7mu}\left(1 + \frac{G_{i,j}\abs{h_{i,j}}^{2}P_{i,j}}{\sigma_{i,j}^{2}}\right){\mkern -5mu}\\[3ex]
\displaystyle Q_{1}D_{i}^{d}W_{j}\ln{\mkern -7mu}\left(1 + \frac{G_{i,j}\abs{h_{i,j}}^{2}P_{i,j}}{\sigma_{i,j}^{2}}\right){\mkern -5mu}; D_{i}^{d} \leq W_{j}\ln{\mkern -7mu}\left(1 + \frac{G_{i,j}\abs{h_{i,j}}^{2}P_{i,j}}{\sigma_{i,j}^{2}}\right){\mkern -5mu} < D_{i}^{d} + D_{i}^{o}\\[3ex]
\displaystyle 0; W_{j}\ln{\mkern -7mu}\left(1 + \frac{G_{i,j}\abs{h_{i,j}}^{2}P_{i,j}}{\sigma_{i,j}^{2}}\right){\mkern -5mu} < D_{i}^{d}
\end{Bmatrix}
\end{equation*}
\end{document}
PS 我添加了geometry
以避免方程进入边缘。
更新
如果希望文档中的所有数学运算都以显示样式书写,可以声明\everymath{\displaystyle}
;
\documentclass{article}
\usepackage{geometry}
\usepackage{mathtools}
\DeclarePairedDelimiter{\abs}{\lvert}{\rvert}
\everymath{\displaystyle}
\begin{document}
\begin{equation*}
V_{i,j} =
\begin{Bmatrix}
(Q_{1}D_{i}^{d} + Q_{2}D_{i}^{o})W_{j}\ln{\mkern -7mu}\left(1 + \frac{G_{i,j}\abs{h_{i,j}}^{2}P_{i,j}}{\sigma_{i,j}^{2}}\right){\mkern -5mu}; D_{i}^{d} + D_{i}^{o} \leq W_{j}\ln{\mkern -7mu}\left(1 + \frac{G_{i,j}\abs{h_{i,j}}^{2}P_{i,j}}{\sigma_{i,j}^{2}}\right){\mkern -5mu}\\[3ex]
Q_{1}D_{i}^{d}W_{j}\ln{\mkern -7mu}\left(1 + \frac{G_{i,j}\abs{h_{i,j}}^{2}P_{i,j}}{\sigma_{i,j}^{2}}\right){\mkern -5mu}; D_{i}^{d} \leq W_{j}\ln{\mkern -7mu}\left(1 + \frac{G_{i,j}\abs{h_{i,j}}^{2}P_{i,j}}{\sigma_{i,j}^{2}}\right){\mkern -5mu} < D_{i}^{d} + D_{i}^{o}\\[3ex]
0; W_{j}\ln{\mkern -7mu}\left(1 + \frac{G_{i,j}\abs{h_{i,j}}^{2}P_{i,j}}{\sigma_{i,j}^{2}}\right){\mkern -5mu} < D_{i}^{d}
\end{Bmatrix}
\end{equation*}
\end{document}
答案4
您必须加载该mathtools
包才能获取multlined
环境。
无论如何,Bmatrix
来自同一个包(以及来自的amsmath
,它mathtools
是一个扩展)的环境可能适合您:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
V_{i,j}=\begin{Bmatrix} Q_1 \\ Q_2 \\ Q_3\end{Bmatrix}
\]
\end{document}
除了Q_1
、Q_2
和Q_3
,您还可以输入自己的公式。