（免责声明：是的，我已经阅读过：嵌套案例、对齐和编号，没有帮助）
我正在尝试得到这样的东西：
和 ：
但编号要对齐。
我通过以下写作获得上述例子：
\begin{align*}
&\mathbf{\dot{x}_s} = \begin{bmatrix}
\mathbf{\ddot{\theta}} & \mathbf{\dot{\theta}} & \mathbf{\ddot{p}} & \mathbf{\dot{p}}
\end{bmatrix}^T = \mathbf{0} \\
\Rightarrow &\begin{cases}
\mathbf{\dot{\theta}} = \mathbf{0} \textrm{\hspace{120pt}(1)}\\
\mathbf{\dot{p}} = \mathbf{0} \textrm{\hspace{120pt}(2)}\\
\mathbf{\ddot{\theta}} = \mathbf{0} \textrm{\hspace{120pt}(3)}\\
\mathbf{\ddot{p}} = \mathbf{0} \textrm{\hspace{120pt}(4)}\\
\end{cases}
\end{align*}
和
\begin{align*}
&\mathbf{\ddot{\theta}} = \mathbf{0} \\
\Rightarrow &\mathbf{\mathcal{I}}^{-1} \cdot \left(-\mathbf{\dot{\theta}} \times \mathbf{\mathcal{I}} \mathbf{\dot{\theta}} + \begin{bmatrix}
M_{\alpha} \\ M_{\beta} \\ M_{\gamma}
\end{bmatrix}\right) = \mathbf{0} \\
\Rightarrow &\begin{cases}
\mathbf{\dot{\theta}} = \mathbf{0} \textrm{\hspace{140pt}(1)}\\
\begin{bmatrix}
M_{\alpha} & M_{\beta} & M_{\gamma}
\end{bmatrix}^T = \mathbf{0}
\end{cases} \textrm{(5)}\\
\end{align*}
我第一次尝试：
\begin{align}
&\mathbf{\dot{x}_s} = \begin{bmatrix}
\mathbf{\ddot{\theta}} & \mathbf{\dot{\theta}} & \mathbf{\ddot{p}} & \mathbf{\dot{p}}
\end{bmatrix}^T = \mathbf{0} \nonumber\\
\Rightarrow &\begin{cases}
\mathbf{\dot{\theta}} = \mathbf{0} \\
\mathbf{\dot{p}} = \mathbf{0} \\
\mathbf{\ddot{\theta}} = \mathbf{0} \\
\mathbf{\ddot{p}} = \mathbf{0} \\
\end{cases}
\end{align}
这导致整个案例环境只有一个数字（不是我想要的）：
和 ：
\begin{empheq}{align*}
&\mathbf{\dot{x}_s} = \begin{bmatrix}
\mathbf{\ddot{\theta}} & \mathbf{\dot{\theta}} & \mathbf{\ddot{p}} & \mathbf{\dot{p}}
\end{bmatrix}^T = \mathbf{0} \\
\Rightarrow &\begin{empheq}[left=\empheqlbrace]{align}
\mathbf{\dot{\theta}} &= \mathbf{0}\\
\mathbf{\dot{p}} &= \mathbf{0} \\
\mathbf{\ddot{\theta}} &= \mathbf{0} \\
\mathbf{\ddot{p}} &= \mathbf{0}
\end{empheq}
\end{empheq}
无法编译。
对于第二个，我甚至没有尝试使它变得更好（对于第一个我做不到，对于第二个也做不到）。
最小示例：
序言：
\documentclass[
10pt,
english,
twoside
]{article}
\usepackage{mathtools}
\setcounter{MaxMatrixCols}{20}
\usepackage{empheq}
主要的 ：
\input{preambule}
\begin{document}
\begin{align}
&\mathbf{\dot{x}_s} = \begin{bmatrix}
\mathbf{\ddot{\theta}} & \mathbf{\dot{\theta}} & \mathbf{\ddot{p}} & \mathbf{\dot{p}}
\end{bmatrix}^T = \mathbf{0} \nonumber\\
\Rightarrow &\begin{cases}
\mathbf{\dot{\theta}} = \mathbf{0} \\
\mathbf{\dot{p}} = \mathbf{0} \\
\mathbf{\ddot{\theta}} = \mathbf{0} \\
\mathbf{\ddot{p}} = \mathbf{0} \\
\end{cases}
\end{align}
\begin{align*}
&\mathbf{\dot{x}_s} = \begin{bmatrix}
\mathbf{\ddot{\theta}} & \mathbf{\dot{\theta}} & \mathbf{\ddot{p}} & \mathbf{\dot{p}}
\end{bmatrix}^T = \mathbf{0} \\
\Rightarrow &\begin{cases}
\mathbf{\dot{\theta}} = \mathbf{0} \textrm{\hspace{120pt}(1)}\\
\mathbf{\dot{p}} = \mathbf{0} \textrm{\hspace{120pt}(2)}\\
\mathbf{\ddot{\theta}} = \mathbf{0} \textrm{\hspace{120pt}(3)}\\
\mathbf{\ddot{p}} = \mathbf{0} \textrm{\hspace{120pt}(4)}\\
\end{cases}
\end{align*}
%\begin{empheq}{align*}
% &\mathbf{\dot{x}_s} = \begin{bmatrix}
% \mathbf{\ddot{\theta}} & \mathbf{\dot{\theta}} & \mathbf{\ddot{p}} & \mathbf{\dot{p}}
% \end{bmatrix}^T = \mathbf{0} \\
%\Rightarrow &\begin{empheq}[left=\empheqlbrace]{align}
% \mathbf{\dot{\theta}} &= \mathbf{0}\\
% \mathbf{\dot{p}} &= \mathbf{0} \\
% \mathbf{\ddot{\theta}} &= \mathbf{0} \\
% \mathbf{\ddot{p}} &= \mathbf{0}
% \end{empheq}
%\end{empheq}
\begin{align*}
&\mathbf{\ddot{\theta}} = \mathbf{0} \\
\Rightarrow &\mathbf{\mathcal{I}}^{-1} \cdot \left(-\mathbf{\dot{\theta}} \times \mathbf{\mathcal{I}} \mathbf{\dot{\theta}} + \begin{bmatrix}
M_{\alpha} \\ M_{\beta} \\ M_{\gamma}
\end{bmatrix}\right) = \mathbf{0} \\
\Rightarrow &\begin{cases}
\mathbf{\dot{\theta}} = \mathbf{0} \textrm{\hspace{140pt}(1)}\\
\begin{bmatrix}
M_{\alpha} & M_{\beta} & M_{\gamma}
\end{bmatrix}^T = \mathbf{0}
\end{cases} \textrm{(5)}\\
\end{align*}
\end{document}
答案1
由于所需结果的屏幕截图没有将第一个关系的等号与其他等号对齐，因此您可以执行以下操作
\documentclass[10pt,english,twoside]{article}
\usepackage{mathtools}
\setcounter{MaxMatrixCols}{20}
\usepackage{empheq}
\begin{document}
\[\hspace{10em}\mathbf{\dot{x}_s} = \begin{bmatrix}
\mathbf{\ddot{\theta}} & \mathbf{\dot{\theta}} & \mathbf{\ddot{p}} & \mathbf{\dot{p}}
\end{bmatrix}^T = \mathbf{0}\]
\vspace*{-\belowdisplayskip}
\begin{empheq}[left=\Rightarrow\empheqlbrace]{align}
\mathbf{\dot{\theta}} &= \mathbf{0}\\
\mathbf{\dot{p}} &= \mathbf{0} \\
\mathbf{\ddot{\theta}} &= \mathbf{0} \\
\mathbf{\ddot{p}} &= \mathbf{0}
\end{empheq}
\begin{align*}
\mathbf{\ddot{\theta}} &= \mathbf{0} \\
\Rightarrow \mathbf{\mathcal{I}}^{-1} \cdot \left(-\mathbf{\dot{\theta}} \times \mathbf{\mathcal{I}} \mathbf{\dot{\theta}} + \begin{bmatrix}
M_{\alpha} \\ M_{\beta} \\ M_{\gamma}
\end{bmatrix}\right) &= \mathbf{0} \hspace{3em}
\end{align*}
\begin{empheq}[left=\Rightarrow\empheqlbrace]{align}
\mathbf{\dot{\theta}} &= \mathbf{0} \\
\begin{bmatrix}
M_{\alpha} & M_{\beta} & M_{\gamma}
\end{bmatrix}^T &= \mathbf{0}
\end{empheq}
\end{document}
