I want to box, as an answer, an equation of the align* environment. Not sure how to do it.
\begin{align*}
(1+2i)z_2&=-11(2-i)\\
z_2&=\dfrac{11(i-2)}{1+2i}\\
z_2&=11i
\end{align*}
I have tried \boxed{z_2&=11i}, but it failed.
Align Environment – Box Part of Equation in LaTeX
alignamsmathboxes
Related Solutions
I'm not sure why but you can't use \begin{align} and \end{align} in the definition of a new environment; you have to use the "lower-level" macros \align and \endalign instead. Edit: as pointed by alexwlchan in his comment, you can find more details about that in section 6 of Technical notes on the amsmath package.
Here I've used the equivalent of an align* environment (see Herbert's answer to Define a custom align, and align* environment).
Note that you will get an error if you try to reset your grammarcounter at each chapter in the article class, because the latter doesn't have chapters; \section is the most high-level sectioning command in the article class. Did you mean
\numberwithin{grammarcounter}{section}
instead?
\documentclass{article}
\usepackage{amsmath}
\newcounter{grammarcounter}[section]
\makeatletter
\newenvironment{grammar}
{%
\refstepcounter{grammarcounter}
\start@align\@ne\st@rredtrue\m@ne
\tag{$\Gamma_{\thegrammarcounter}$}
}{%
\endalign
}
\makeatother
\begin{document}
\section{Foo}
\begin{grammar}
\label{gr:label}
E &::= E + E \\
E &::= a \\
E &::= b
\end{grammar}
\begin{grammar}
\label{gr:label2}
E &::= E + E \\
E &::= a \\
E &::= b
\end{grammar}
\end{document}
Two options; the first one using the empheq package, and the second one using the interaction between empheq and tcolorbox for fancyer designs:
The code:
\documentclass{article}
\usepackage{amsmath}
\usepackage[many]{tcolorbox}
\usepackage{empheq}
\usetikzlibrary{shadows}
\tcbset{
highlight math style={
enhanced,
colframe=red!60!black,
colback=yellow!50,
arc=4pt,
boxrule=1pt,
drop fuzzy shadow
}
}
\begin{document}
\begin{empheq}[box=\fbox]{align}
a&=\sin(z)\\
E&=mc^2 + \int_a^b x\, dx
\end{empheq}
\begin{empheq}[box=\tcbhighmath]{align}
a&=\sin(z)\\
E&=mc^2 + \int_a^b x\, dx
\end{empheq}
\end{document}
Best Answer
You can use the
\Aboxedmacro from themathtoolspackage to have a box around a single alignment point&, i.e. a single line in your case: