Stanley wrote:
>I'm legally blind, so it's much easier to use the computer than to attempt to write directly. I would like to box the last line of a multiline equation set (homework problems). I would like the box to be aligned with the "=" sign like the rest of the equations, but I haven't figured out how to do that without breaking things. Here's what I currently have, which will work, if there is no simple way to do what I'd like:
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Here is an example I found on comp.text.tex; I usually just read from
this group since they are a little hard on people who don't research first.
http://groups.google.com/groups?hl=en&lr=&ie=UTF8&oe=UTF8&group=comp.text.tex
\documentclass{article}
\usepackage{amsmath}
\newlength{\testwidth}
\newsavebox{\tempbox}
% This command sets back the equation counter and then readvances it,
% in order to reset the current label string after our strange use of
% \tag* has corrupted it with lots of extra junk.
%
\newcommand{\relabel}[1]{%
\addtocounter{equation}{1}%
\refstepcounter{equation}%
\label{#1}%
}
\begin{document}
Here is a test boxing the last line, including the equation number:
%
% Create the frame ahead of time; make it overlap to the left by using
% the [r] placement option with a width of zero.
%
\savebox{\tempbox}[0pt][r]{
%
% Print a box around an invisible space of the current width
% (adjusting for fboxsep on both sides), and a vphantom of the tallest
% element (to get the correct height).
%
\boxed{\hspace{2\fboxsep}\hspace{\linewidth}%
\vphantom{\frac{\sin(\omega T)}{\omega T}}%
}%
}%
\begin{align*}
X_1(j\omega) & = \int\limits^{+\infty}_{\infty} x_1(t) e^{j\omega
t} dt \\
& = \frac{v_o}{j\omega T} \left[e^{j\omega t}\right]^T_{T} \\
& = \frac{v_o}{j\omega T} \left( 2 j \sin (\omega T) \right) \\
X_1(j\omega) & = 2v_o \frac{\sin(\omega T)}{\omega T}
%
% We need to use \tag*, but that doesn't change the equation counter, so
% we increment the counter by hand. Getting the label right takes more
% work, see below.
%
\stepcounter{equation}
\tag*{(\theequation)% Normal equation number
\hspace{\fboxsep}\usebox{\tempbox}%
}
\relabel{eq1}
\end{align*}
And a second test for boxing only the equation body, not the number.
This time we can use \texttt{align} and \verb'\notag' because
\verb'\tag*' is not necessary.
\begin{align}
X_1(j\omega) & = \int\limits^{+\infty}_{\infty} x_1(t) e^{j\omega
t} dt \notag\\
& = \frac{v_o}{j\omega T} \left[e^{j\omega t}\right]^T_{T} \notag\\
& = \frac{v_o}{j\omega T} \left( 2 j \sin (\omega T) \right) \notag\\
% Skip to the righthand column, see below.
&
%
% Measure the width of the lefthand side, including some adjustments
% for the frame.
%
\settowidth{\testwidth}{\hspace{\fboxrule}\hspace{\fboxsep}$X_1(j\omega)$}
%
% Print the lefthand side and the righthand side together in the
% *righthand column* with negative space to shift it to the left.
%
\hspace{\testwidth}%
%
% And now we can use amsmath's \boxed command which is just \fbox for
% math with \displaystyle.
%
\boxed{X_1(j\omega) = 2v_o \frac{\sin(\omega T)}{\omega T}}
\end{align}
\end{document}
