I'd like to know if it's possible to increase the thickness of a brace.
The code
\documentclass[oneside]{article}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\newcommand{\ve}{\textbf}
\newcommand{\veu}{\ve u}
\newcommand{\vev}{\ve v}
\begin{document}
\begin{equation}
\begin{cases}
q_1(\veu) \land q_1(\vev) &= \begin{vmatrix}
u_2 & v_2\\
u_3 & v_3
\end{vmatrix} = u_2v_3 - u_3v_2 = 0\\[1.5em]
q_2(\veu) \land q_2(\vev) &= \begin{vmatrix}
u_1 & v_1\\
u_3 & v_3
\end{vmatrix} = u_1v_3 - u_3v_1 = 0\\[1.5em]
q_3(\veu) \land q_3(\vev) &= \begin{vmatrix}
u_1 & v_1\\
u_3 & v_3
\end{vmatrix} = u_1v_3 - u_3v_1 = 0
\end{cases}
\end{equation}
\end{document}
The result

I think the brace is a bit too thin, and I tried to replace cases with a manual \left\{ but that didn't work.
casesalready use\left\{so it will not help much. – daleif Mar 04 '15 at 09:24amsmathelements andamsmathis not loaded in your example. I would not bother with an issue like this. Braces look different in different fonts. – daleif Mar 04 '15 at 09:30amsmath. Short of writing your own brace usingtikzI don't think it this is worth improving. – daleif Mar 04 '15 at 09:33amsmath. I am using many packages, so I forgot about it. So are you saying there is nothing to do? – rubik Mar 04 '15 at 09:40\mathbfand not\bmfrom thebmpackage? I personally like italic bold face better than upright bold face for vectors. – daleif Mar 04 '15 at 10:08