将一个案例的括号与另一个案例的括号匹配

Question

cases在同一环境中，如何匹配两条线equation？我遇到的情况是：

\begin{equation}
\begin{rcases}
  \sum_{I=1}^{NP} K_h (x - x_I; x) \Delta x_I &= 1 \\
  \sum_{I=1}^{NP} \left(\frac{x - x_I}{h}\right) K_h (x - x_I; x) \Delta x_I &= 0 \\
  &\;\;\vdots \notag \\q
  \sum_{I=1}^{NP} \left(\frac{x - x_I}{h}\right)^n K_h (x - x_I; x) \Delta x_I &= 0
\end{rcases} =  
\begin{cases}
  M_0 (x) &= 1 \\
  M_1 (x) &= 1 \\
  &\;\;\vdots \notag \\
  M_n (x) &= 1 \\
\end{cases}
\end{equation}

这是当前输出：

现在我想将左侧的案例行与右侧的案例行进行匹配。我可以做一些丑陋的事情，比如添加\vspace，但有没有更优雅的方式来做到这一点？

Answer 1

如果希望<stuffB>与 具有相同的高度<stuffA>，请使用\vphantom{<stuffA>}<stuffB>：

\documentclass{article}

\usepackage{mathtools,array}

\begin{document}

\begin{equation}
  \left. \begin{array}{>{\displaystyle}r}
    \sum_{I = 1}^{NP} K_h (x - x_I; x) \Delta x_I = 1 \\
    \sum_{I = 1}^{NP} \Bigl( \frac{x - x_I}{h} \Bigr) K_h (x - x_I; x) \Delta x_I = 0 \\
    \vdotswithin{=}\phantom{0} \\
    \sum_{I = 1}^{NP} \Bigl(\frac{x - x_I}{h} \Bigr)^n K_h (x - x_I; x) \Delta x_I = 0
  \end{array} \right\} 
  = 
  \left\{\begin{array}{>{\displaystyle}r}
    \vphantom{\sum_{I = 1}^{NP}} M_0 (x) = 1 \\
    \vphantom{\sum_{I = 1}^{NP}} M_1 (x) = 1 \\
    \vdotswithin{=}\phantom{1} \\
    \vphantom{\sum_{I = 1}^{NP}} M_n (x) = 1
  \end{array}\right.
\end{equation}

\end{document} 

Answer 2

aligned这是一个使用两种环境以及（印刷）支柱的解决方案。

\documentclass{article}
\usepackage{mathtools} % for \vdotswithin macro
\usepackage{mleftright} \mleftright % tighter spacing around large parentheses
\newcommand\tallstrut{\vphantom{\sum_{I=1}^{NP}}} % define a tall typographic strut

\begin{document}
\begin{equation}
\left.
\begin{aligned}
  \sum_{I=1}^{NP} K_h (x - x_I; x) \Delta x_I &= 1 \\
  \sum_{I=1}^{NP} \left(\frac{x - x_I}{h}\right) K_h (x - x_I; x) \Delta x_I &= 0 \\
  &\vdotswithin{=} \\
  q\sum_{I=1}^{NP} \left(\frac{x - x_I}{h}\right)^{\!n} K_h (x - x_I; x) \Delta x_I &= 0
\end{aligned} 
\right\} 
=  
\left\{
\begin{aligned}
  M_0 (x) &= 1  \tallstrut \\
  M_1 (x) &= 1  \tallstrut \\
          &\vdotswithin{=} \\
  M_n (x) &= 1  \tallstrut 
\end{aligned}
\right.
\end{equation}
\end{document}