# Thickness of Brackets and Parentheses

I try to make all the brackets and parentheses to have the same thickness.

Normally, the thickness of brackets and parentheses depends on how many lines of array and thing you will have inside them. For example, the following code is the notation of the matrix.

\documentclass[letterpaper]{article}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{mathrsfs}
\usepackage{mathtools}
\usepackage{commath}
\usepackage{graphicx}
\usepackage{chngcntr}
\usepackage{xcolor}
\usepackage{ulem}

\begin{document}

\begin{align*}
A = \left[ a_{ij} \right] =
\left[
\begin{matrix}
a_{11} & a_{12} & \ldots & a_{1n} \\
a_{21} & a_{22} & \ldots & a_{2n} \\
\vdots & \vdots & \ddots & \vdots \\
a_{m1} & a_{m2} & \ldots & a_{mn}
\end{matrix}
\right]
\end{align*}
\vspace{2mm}

\end{document}


You can see that for the aij only and the matrix, the thicknesses of square brackets are not the same. Is there a way to control this? I love having the consistency in my work.

I've faced this problem as well and the only way I found to overcome this was to change the font. Using the code in manooooh's answer didn't work either, the bracket still gets thicker.

If you include \usepackage{kpfonts} in your code, the brackets should have the same thickness (at least to me, its the same). On the other hand, the numbers look a little odd to me, so I'd choose a different one. Take a look here, in the font catalogue, and maybe you can find one that suits you best.

I know it doesn't answer the problem in the way you wanted, but unfortunately, I don't think that it is possible to do that.

In lieu of searching for fonts, I suggest using an unbracketed matrix (amsmath) and then vertically scaling (graphicx) ordinary-sized brackets around it , using \scalebox{<widthfactor>}{<heightfactor>}{<content>}:

\usepackage{amsmath}
\usepackage{graphicx}
\begin{document}

\begin{align*}
A = $a_{ij}$ =
\scalebox{1.0}{3.0}{\[}
\begin{matrix}
a_{11} & a_{12} & \ldots & a_{1n} \\
a_{21} & a_{22} & \ldots & a_{2n} \\
\vdots & \vdots & \ddots & \vdots \\
a_{m1} & a_{m2} & \ldots & a_{mn}
\end{matrix}
\scalebox{1.0}{3.0}{\[}
\end{align*}
\vspace{2mm}

\end{document}


Addendum: Just to be clear, this will thicken the horizontal lines at the ends of the brackets. Vertical strokes would be unaffected.

A thought on fonts: try a vector-linear font, like an engraving font, to use for the brackets, since thickness should not scale with size, or should be controllable with whatever macros would determine lineweight with such a font.