Latex 方程中的新行

Question

  \begin{equation}
    S=\sum\limits_{i=1}^{8}A_i
    S=\sum\limits_{i=1}^{8}B_i
    S=\sum\limits_{i=1}^{8}C_i
    S=\sum\limits_{i=1}^{8}D_i
  \end{equation}

考虑到上述代码，我非常感兴趣的是，如何才能打印这 4 个方程式，每行一个，而不是全部放在一行中。

Answer 1

该包amsmath为方程式提供了许多环境，例如：

• gather默认为中心方程
• align，允许垂直对齐

例子：

\documentclass{article}
\usepackage{amsmath}

\begin{document}
  \begin{gather}
    S=\sum_{i=1}^{8}A_i\\
    S=\sum_{i=1}^{8}B_i\\
    S=\sum_{i=1}^{8}C_i\\
    S=\sum_{i=1}^{8}D_i
  \end{gather}
  \begin{align}
    S &= \sum_{i=1}^{8}A_i\\
    S &= \sum_{i=1}^{8}B_i\\
    S &= \sum_{i=1}^{8}C_i\\
    S &= \sum_{i=1}^{8}D_i
  \end{align}
\end{document}

最后一行的方程式编号

\documentclass{article}
\usepackage{amsmath}

\begin{document}
  \begin{gather}
    \nonumber S=\sum_{i=1}^{8}A_i\\
    \nonumber S=\sum_{i=1}^{8}B_i\\
    \nonumber S=\sum_{i=1}^{8}C_i\\
    S=\sum_{i=1}^{8}D_i
  \end{gather}
  \begin{align}
    \nonumber S &= \sum_{i=1}^{8}A_i\\
    \nonumber S &= \sum_{i=1}^{8}B_i\\
    \nonumber S &= \sum_{i=1}^{8}C_i\\
    S &= \sum_{i=1}^{8}D_i
  \end{align}
\end{document}

中间的方程式编号

\documentclass{article}
\usepackage{amsmath}

\begin{document}
  \begin{equation}
  \begin{gathered}
    S=\sum_{i=1}^{8}A_i\\
    S=\sum_{i=1}^{8}B_i\\
    S=\sum_{i=1}^{8}C_i\\
    S=\sum_{i=1}^{8}D_i
  \end{gathered}
\end{equation}
\begin{equation}
  \begin{aligned}
    S &= \sum_{i=1}^{8}A_i\\
    S &= \sum_{i=1}^{8}B_i\\
    S &= \sum_{i=1}^{8}C_i\\
    S &= \sum_{i=1}^{8}D_i
  \end{aligned}
\end{equation}
\end{document}

附录：带案例的符号函数定义

\documentclass{article}
\usepackage{amsmath}
\usepackage{colonequals}

\DeclareMathOperator{\sgn}{sgn}

\begin{document}
  \begin{equation}
    \sgn(x) \colonequals
    \begin{cases}
      -1 & \text{if } x < 0 \\
      0  & \text{if } x = 0 \\
      1  & \text{if } x > 0
    \end{cases}
  \end{equation}
\end{document}

Answer 2

您还可以每行有多个对齐点。对于每个组一个数字，请使用嵌套环境：（如果您加载而不是，则gathered, aligned, multlined使用后者）。您还可以使用环境（1a、1b 等）：mathtoolsamsmathsubnumberingsubequations

\documentclass{article}
\usepackage{mathtools}
\usepackage{showframe}

\begin{document}
  \begin{align}
    S &= \sum_{i=1}^{8}A_i &S &= \sum_{i=1}^{8}B_i\\
    S &= \sum_{i=1}^{8}C_i & S &= \sum_{i=1}^{8}D_i
  \end{align}

  \begin{flalign}
    S &= \sum_{i=1}^{8}A_i &S &= \sum_{i=1}^{8}B_i & S &= \sum_{i=1}^{8}C_i \\
    S &= \sum_{i=1}^{8}D_i & S &= \sum_{i=1}^{8}D_i & S &= \sum_{i=1}^{8}F_i
  \end{flalign}

  \begin{align*}
    S &= \sum_{i=1}^{8}A_i &S &= \sum_{i=1}^{8}B_i & S &= \sum_{i=1}^{8}C_i \\
    S &= \sum_{i=1}^{8}D_i & S &= \sum_{i=1}^{8}D_i & S &= \sum_{i=1}^{8}F_i
  \end{align*}

\begin{equation}\label{myeq}
      \begin{aligned}
        S &= \sum_{i=1}^{8}A_i &S &= \sum_{i=1}^{8}B_i\\
        S &= \sum_{i=1}^{8}C_i & S &= \sum_{i=1}^{8}D_i
      \end{aligned}
\end{equation}
\end{document}

Answer 3

或者

\documentclass{amsart}

\begin{document}


\begin{gather}
\left\{
\begin{aligned}
    S &=\sum\limits_{i=1}^{8}A_i,\\
    S&=\sum\limits_{i=1}^{8}B_i,\\
    S&=\sum\limits_{i=1}^{8}C_i,\\
    S&=\sum\limits_{i=1}^{8}D_i.
  \end{aligned}
  \right.
  \end{gather}

  \end{document}