大括号内为方程式

Question

big bracket我怎样才能像照片中那样在方程式旁边添加？下面是我的方程式代码。

\begin{align}
\frac{dS_d}{dt}&= A + \lambda_dR_d + \sigma_d(1-\gamma_d)E_d -\beta_dS_dI_d- (m_d+k_d+c_d)S_d \nonumber \\
\frac{dE_d}{dt}&= \beta_dS_dI_d -(m_d+\sigma_d+c_d)E_d \nonumber \\
\frac{dI_d}{dt}&= \sigma_d\gamma_dE_d -(m_d+\mu_d+c_d)I_d \nonumber \\
\frac{dV_d}{dt}&= k_dS_d -(m_d+\lambda_d)V_d \nonumber \\
\frac{dS_h}{dt}&= B + \lambda_hR_h + \sigma_h(1-\gamma_h)E_h -\beta_hS_hI_d- m_hS_h \\
\frac{dE_h}{dt}&= \beta_hS_hI_d -(m_h+\sigma_h+k_h)E_h \nonumber \\
\frac{dI_h}{dt}&= \sigma_h\gamma_hE_h -(m_h+\mu_h)I_h \nonumber \\
\frac{dV_h}{dt}&= k_hE_h -(m_h+\lambda_h)V_h \nonumber \\
\end{align}

Answer 1

另一个变体，也基于 empheq（加载mathtools），但与环境的行间距不太紧密spreadlines。

顺便说一句，不要以 ; 结束多行环境\\，如果环境有编号，它会为空行添加一个数字，以及不需要的垂直间距。

\documentclass{article}

\usepackage{empheq}

\begin{document}

\begin{spreadlines}{8pt}
\begin{empheq}[left =\empheqlparen]{equation}
\begin{aligned}
\frac{dS_d}{dt}&= A + \lambda_dR_d + \sigma_d(1-\gamma_d)E_d -\beta_dS_dI_d- (m_d+k_d+c_d)S_d \\
\frac{dE_d}{dt}&= \beta_dS_dI_d -(m_d+\sigma_d+c_d)E_d \\
\frac{dI_d}{dt}&= \sigma_d\gamma_dE_d -(m_d+\mu_d+c_d)I_d \\
\frac{dV_d}{dt}&= k_dS_d -(m_d+\lambda_d)V_d \\
\frac{dS_h}{dt}&= B + \lambda_hR_h + \sigma_h(1-\gamma_h)E_h -\beta_hS_hI_d- m_hS_h \\
\frac{dE_h}{dt}&= \beta_hS_hI_d -(m_h+\sigma_h+k_h)E_h \\
\frac{dI_h}{dt}&= \sigma_h\gamma_hE_h -(m_h+\mu_h)I_h \\
\frac{dV_h}{dt}&= k_hE_h -(m_h+\lambda_h)V_h 
\end{aligned}
\end{empheq}
\end{spreadlines}

\end{document} 

Answer 2

添加\left(和\right.，但使用equation和aligned：

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{equation}
\left(
\begin{aligned}
\frac{dS_d}{dt}&= A + \lambda_dR_d + \sigma_d(1-\gamma_d)E_d -\beta_dS_dI_d- (m_d+k_d+c_d)S_d \\[0.5ex]
\frac{dE_d}{dt}&= \beta_dS_dI_d -(m_d+\sigma_d+c_d)E_d \\[0.5ex]
\frac{dI_d}{dt}&= \sigma_d\gamma_dE_d -(m_d+\mu_d+c_d)I_d \\[0.5ex]
\frac{dV_d}{dt}&= k_dS_d -(m_d+\lambda_d)V_d \\[0.5ex]
\frac{dS_h}{dt}&= B + \lambda_hR_h + \sigma_h(1-\gamma_h)E_h -\beta_hS_hI_d- m_hS_h \\[0.5ex]
\frac{dE_h}{dt}&= \beta_hS_hI_d -(m_h+\sigma_h+k_h)E_h \\[0.5ex]
\frac{dI_h}{dt}&= \sigma_h\gamma_hE_h -(m_h+\mu_h)I_h \\[0.5ex]
\frac{dV_h}{dt}&= k_hE_h -(m_h+\lambda_h)V_h
\end{aligned}
\right.
\end{equation}

\end{document}

如您所见，方程编号居中，无需任何猜测。

Answer 3

使用该empheq套件，您可以满足您的期望：

\documentclass{article}
\usepackage{empheq}
\begin{document}

\begin{empheq}[left=\empheqbiglparen]{align}
\frac{dS_d}{dt}&= A + \lambda_dR_d + \sigma_d(1-\gamma_d)E_d -\beta_dS_dI_d- (m_d+k_d+c_d)S_d \nonumber \\
\frac{dE_d}{dt}&= \beta_dS_dI_d -(m_d+\sigma_d+c_d)E_d \nonumber \\
\frac{dI_d}{dt}&= \sigma_d\gamma_dE_d -(m_d+\mu_d+c_d)I_d \nonumber \\
\frac{dV_d}{dt}&= k_dS_d -(m_d+\lambda_d)V_d \nonumber \\
\frac{dS_h}{dt}&= B + \lambda_hR_h + \sigma_h(1-\gamma_h)E_h -\beta_hS_hI_d- m_hS_h \\
\frac{dE_h}{dt}&= \beta_hS_hI_d -(m_h+\sigma_h+k_h)E_h \nonumber \\
\frac{dI_h}{dt}&= \sigma_h\gamma_hE_h -(m_h+\mu_h)I_h \nonumber \\
\frac{dV_h}{dt}&= k_hE_h -(m_h+\lambda_h)V_h \nonumber
\end{empheq}

\end{document}

Answer 4

在 LaTeXer 的答案的基础上，还有(扩展了)dcases提供的环境。它的优点是所有方程式默认都处于显示模式。mathtools packageamsmath

\documentclass{article}
\usepackage{mathtools}
\begin{document}
\begin{align}
  \begin{dcases}
    \frac{dS_d}{dt} = A + \lambda_dR_d + \sigma_d(1-\gamma_d)E_d -\beta_dS_dI_d- (m_d+k_d+c_d)S_d \\
    \frac{dE_d}{dt} = \beta_dS_dI_d -(m_d+\sigma_d+c_d)E_d \\
    \frac{dI_d}{dt} = \sigma_d\gamma_dE_d -(m_d+\mu_d+c_d)I_d \\
    \frac{dV_d}{dt} = k_dS_d -(m_d+\lambda_d)V_d \\
    \frac{dS_h}{dt} = B + \lambda_hR_h + \sigma_h(1-\gamma_h)E_h -\beta_hS_hI_d- m_hS_h \\
    \frac{dE_h}{dt} = \beta_hS_hI_d -(m_h+\sigma_h+k_h)E_h \\
    \frac{dI_h}{dt} = \sigma_h\gamma_hE_h -(m_h+\mu_h)I_h \\
    \frac{dV_h}{dt} = k_hE_h -(m_h+\lambda_h)V_h \\
  \end{dcases}
\end{align}
\end{document}