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I would really like to get a multiline equation with text explaining each step.

I've got close with

    A \simeq & B  \mbox{[Lemma 8.35(iii)]} \\
      \simeq & C \mbox{[exactness of first column - see Ex. 5.3]} \\
\end{equation*} `

But I can't get tab spacing between the equation and the message box. Maybe an mbox is not the best way?

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up vote 6 down vote accepted

The amsmath package offers a number of environments that can achieve what you want: here's an example (with annotations flushed right, and with annotations two quads appart from the equations):



    A & \simeq B  \tag{[Lemma 8.35(iii)]} \\
        & \simeq C  \tag{[exactness of first column - see Ex. 5.3]}
\end{align*} `

  A &\simeq B   &\qquad & \text{[Lemma 8.35(iii)]} \\
      &\simeq C   &\qquad & \text{[exactness of first column - see Ex. 5.3]}
\end{alignat*} `

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thanks for the help – Qwirk Mar 31 '11 at 1:51

You can also use intertext for short annotations of 1-2 lines.


see 3.10 Interrupting a display in amsmath

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amstex is, these days, mostly of historical interest. however, it was the basis for ams-latex, specifically amsmath, and the section 3.10 to which you refer is in the manual for amsmath. texdoc amsldoc if you are working with a tex live system. – barbara beeton Dec 15 '12 at 20:49
Thank you... there is always enough time to make typos. ;-) – Jonas Stein Dec 15 '12 at 21:10

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