# How to express simplification of an array

How can I type the curly bracket and put the expression alongside of it? Basically, I want to simplify the array and $\mathbf{b} = [b_1,b_2]$

I want help to get the following output as in the picture So, the next step would be a new array containing 3 rows instead of 4 rows where the last element of the new array would be $\frac{\partial^2 F}{\partial^2 \mathbf{b}}$

I am using WinEdit7 and MikTex on Windows 7.

• Welcome to Tex.Stackexchange! – user36296 Apr 17 '17 at 20:27

It can be done with a ton of visual formatting, but I'd prefer the second way I propose, which is, in my opinion, clear enough.

\documentclass{article}
\usepackage{amsmath}

\DeclareMathOperator{\RE}{Re}
\DeclareMathOperator{\IM}{Im}

\begin{document}

\begin{equation*}
\begin{bmatrix}
\dfrac{\partial^2 F}{\partial^2\RE{a}} \$3ex] \dfrac{\partial^2 F}{\partial^2\IM{a}} \\[3ex] \begin{matrix} \dfrac{\partial^2 F}{\partial^2 b_1} \\[3ex] \dfrac{\partial^2 F}{\partial^2 b_2} \end{matrix} \rlap{% \quad \displaystyle \left. \vphantom{% \begin{matrix} \dfrac{\partial^2 F}{\partial^2 b_1} \\[3ex] \dfrac{\partial^2 F}{\partial^2 b_2} \end{matrix}% }\right\rbrace \dfrac{\partial^2 F}{\partial^2 \mathbf{b}} \quad where \mathbf{b}=\begin{bmatrix} b_1 & b_2 \end{bmatrix}% } \end{bmatrix} \hphantom{% \displaystyle \left. \vphantom{% \begin{matrix} \dfrac{\partial^2 F}{\partial^2 b_1} \\[3ex] \dfrac{\partial^2 F}{\partial^2 b_2} \end{matrix}% }\right\rbrace \dfrac{\partial^2 F}{\partial^2 \mathbf{b}} \text{\quad where \mathbf{b}=\begin{bmatrix} b_1 & b_2 \end{bmatrix}}% } \end{equation*} \begin{equation*} \begin{bmatrix} \dfrac{\partial^2 F}{\partial^2\RE{a}} \\[3ex] \dfrac{\partial^2 F}{\partial^2\IM{a}} \\[3ex] \dfrac{\partial^2 F}{\partial^2 b_1} \\[3ex] \dfrac{\partial^2 F}{\partial^2 b_2} \end{bmatrix} = \begin{bmatrix} \dfrac{\partial^2 F}{\partial^2\RE{a}} \\[3ex] \dfrac{\partial^2 F}{\partial^2\IM{a}} \\[3ex] \dfrac{\partial^2 F}{\partial^2 \mathbf{b}} \end{bmatrix} \qquad \text{where \mathbf{b}=\begin{bmatrix} b_1 & b_2 \end{bmatrix}} \end{equation*} \end{document} Maybe the bigdelim package could be of help: \documentclass{article} \usepackage{amsmath} \usepackage{bigdelim} \begin{document} \[ \begin{array}{c} \ldelim[{4}{*} a \rdelim]{4}{*}\\ b\\ c\\ d \end{array} \hspace*{-0.4cm} \begin{array}{l} \\ \\ \rdelim\}{2}{*}[\Rightarrow \frac{\partial^2 F}{\partial^2 b} \quad \text{ where } b=...]\\ \\ \end{array}$

\end{document} 