Math & Science ⇒ Large box around a part of an equation ?

[Cham]

I just came across a new problem that I didn't had before, for my usual documents. I now need to show a calculation on several lines (using the align environment), then emphasize the end result on the last line with a large box around it. How to achieve this ?

Here's a MWE code to work with :

Code: Select all

\documentclass[12pt,letterpaper]{article}
\usepackage{amsmath}
\usepackage{empheq}

\begin{document}

Test :

	\begin{align}
		3d + 7 y - 3 x &= aba \nonumber \\[12pt]
		&= 32g hy - \frac{1}{2} \, x y 
	\end{align}

\end{document}

In my usual documents, I simply put the whole equation inside a box using the following code in the preamble :

Code: Select all

\newenvironment{important}[2][]{
	\setkeys{EmphEqEnv}{#2}
	\setkeys{EmphEqOpt}{box={\setlength{\fboxsep}{10pt}\fcolorbox{black}{gray}},#1}
	\EmphEqMainEnv}
{\endEmphEqMainEnv}

However, this would not work for a part of an align display. How could I enclose the last part (after the equal sign) inside a large box ?

[Cham]

Doh ! Apparently, the simple command \boxed{} do the trick !

Is there another way in doing this ? Maybe with a color background inside the box ?

[cgnieder]

You can have fancy boxes with tcolorbox and its theorems library:

Code: Select all

\documentclass[12pt,letterpaper]{article}
\usepackage{amsmath}
\usepackage{tcolorbox}
\tcbuselibrary{theorems}

\begin{document}

Test :

\begin{align}
  3d + 7 y - 3 x &= aba \nonumber \\[12pt]
                 &= \tcboxmath{32g hy - \frac{1}{2} \, x y}
\end{align}

\end{document}

Regards

[Cham]

Wow ! This box is nice, thanks ! Maybe a bit too big, though. I'll check the documentation.

[cgnieder]

Maybe a bit too big, though. I'll check the documentation.

tcolorbox has so many possibilities customization that I have no doubt the box can be adapted to whatever you wish.