1

I want to write an equation with bold extended brackets.

For example:

\begin{equation}
x_k = \left[\begin{matrix} 1 & T_s & \displaystyle \dfrac{T_s^2}{2} \\ 0 & 1 & T_s \\ 0 & 0 & 1\end{matrix}\right] x_{k-1} + \xi 
\end{equation}

But I can't obtain bold brackets ([ and ]).

Thank you for helping.

cxix_legio
  • 13

2 Answers2

2

Not sure what the purpose is, but…

\documentclass{article}
\usepackage{amsmath}

\DeclareFontFamily{OMX}{cmexb}{}
\DeclareFontShape{OMX}{cmexb}{b}{n}{<->cmexb10}{}
\DeclareSymbolFont{boldoperators}{OT1}{\familydefault}{b}{n}
\DeclareSymbolFont{boldlargesymbols}{OMX}{cmexb}{b}{n}
\DeclareMathDelimiter{\lbrackbold}{\mathopen} {boldoperators}{"5B}{boldlargesymbols}{"02}
\DeclareMathDelimiter{\rbrackbold}{\mathclose}{boldoperators}{"5D}{boldlargesymbols}{"03}

\makeatletter
\newenvironment{boldbmatrix}{\left\lbrackbold\env@matrix}{\endmatrix\right\rbrackbold}
\makeatother

\begin{document}

\[
\begin{boldbmatrix}
1 & 1 & 1 \\
1 & 1 & 1 \\
1 & 1 & 1
\end{boldbmatrix}
\quad
\begin{bmatrix}
1 & 1 & 1 \\
1 & 1 & 1 \\
1 & 1 & 1
\end{bmatrix}
\]

\end{document}

enter image description here

egreg
  • 1,121,712
1

Do you prefer this type of bold big braces or more bigger than \Bigg? Here there is a minimal working example with a specific screenshot.

enter image description here

%% Compile and read me!
\documentclass[a4paper,12pt]{article}
\usepackage{amsmath,amssymb}
\usepackage{bm}
\SetSymbolFont{largesymbols}{bold}{OMX}{txex}{b}{n} %%%% >--- see the link https://latex.org/forum/viewtopic.php?t=27058
\begin{document}
\begin{equation}
x_k = \bm{\Bigg[}\begin{matrix} 1 & T_s & \frac{T_s^2}{2} \\ 0 & 1 & T_{s} \\ 0 & 0 & 1\end{matrix}\bm{\Bigg]} x_{k-1} + \xi 
\end{equation}
\end{document}

If you use scalerel package created by @Steven B. Segletes with the option scaleobj you can obtain:

enter image description here

\documentclass[a4paper,12pt]{article}
\usepackage{amsmath,amssymb}
\usepackage{bm}
\usepackage{scalerel}
\SetSymbolFont{largesymbols}{bold}{OMX}{txex}{b}{n} 
\begin{document}
\begin{equation}
x_k = \scaleobj{1.2}{\bm{\Bigg[}}\begin{matrix} 1 & T_s & T_s^2/2 \\ 0 & 1 & T_{s} \\ 0 & 0 & 1\end{matrix}\scaleobj{1.2}{\bm{\Bigg]}}\,x_{k-1} + \xi 
\end{equation}
\end{document}
Sebastiano
  • 54,118