Formatting Equation Numbers

Question

I need the numbers of equations and brackets around to be in bold. Doing like this

\usepackage{etoolbox}
\pretocmd{\theequation}{\bf}{}{}

only the number is produced in bold, how to bold brackets?

And second question. I want my references to equations also to be with bolded brackets automatically, how to do this?

Answer 1

You can redefine \tagform@#1 from amsmath.sty:

\documentclass{article}
\usepackage{amsmath}

\makeatletter
\def\tagform@#1{\maketag@@@{\bfseries[\ignorespaces#1\unskip\@@italiccorr]}}
\makeatother

\begin{document} 

\begin{equation}\label{eq:test}
a = b.
\end{equation}
As we see from equation~\eqref{eq:test}... 

\end{document}

Answer 2

The »mathtools« package can do this job for you.

% !TeX program = pdflatex
\documentclass[11pt]{article}
\usepackage[T1]{fontenc}
\usepackage{mathtools}   % loads »amsmath«

\begin{document}
  \newtagform{bbrackets}[\textbf]{\textbf{[}}{\textbf{]}}
  \usetagform{bbrackets}
  \begin{equation}
    a^2+b^2=c^2
  \end{equation}
\end{document}