# The multi-line equation with explanation is too wide

The original question provides a good answer for how to add explanations to the multi-line equations. However, my problem is that the explanations have too long space to the corresponding equations, so they often extend to the margin of page. How can I narrow the space between the equations and their explanations?

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For the odd occasion where your align comment spans multiple lines, consider using a [t]op aligned \parbox of fixed width:

\documentclass{article}
\usepackage{amsmath,lipsum}% http://ctan.org/pkg/{amsmath,lipsum}
\begin{document}
\begin{align*}
A &= B \\
&= C && \text{Because of D} \\
&= D && \parbox[t]{0.7\linewidth}{\raggedright\lipsum*[2]} \\
&= F
\end{align*}
\end{document}

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Is it possible to use \tag{} for this question? –  please stop stalking Apr 1 '13 at 23:00
@Karl'sstudents: The \tag will appear on the same line as the math content. –  Werner Apr 2 '13 at 14:25
@Werner: excuse me. the explanation in your case seems to come from the external document. I tried to delete the \raggedright\lipsum*[2] and replace it with my own explanation, but the explanation will extend to nowhere. Could you explain it further? I am really new to latex... –  user26362 Apr 3 '13 at 6:25
@user26362: What does your explanation look like? Is it paragraph text? You could edit your question to include what you've tried thus far. –  Werner Apr 3 '13 at 6:30
@Werner: I thought I made a silly move: keep typing "afadfadfd" so the explanation will extend out. But, if I tried to type some complete sentences, they became a paragraph. Thank you very much! :) –  user26362 Apr 4 '13 at 2:09

Try the alignat environment. You can find the details in mathmode.pdf.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{alignat*}{2}
A &= B \\
&= C &\quad& \text{Because of D} \\
&= D && \text{But beware of E} \\
&    && \text{Some more on that} \\
&= F &&
\end{alignat*}
\end{document}

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