I'm looking to do the following automatically rather than manually
\documentclass{article}
\usepackage{amsmath}
\begin{document}
These equations are pretty important.
\begin{align}
\label{eqn:one} a+b&=c\\
\label{eqn:two} d+e&=f\\
\label{eqn:three} g+h&=i
\end{align}
But as it turns out, we can actually do better by recalling
that $a=1$, so we have
\begin{equation*}
\tag{\ref{eqn:one}A}
1+b=c\\
\end{equation*}
Furthermore, $c=d=e=2$, so we have
\begin{align*}
\tag{\ref{eqn:one}B} 1+b&=2\\
\tag{\ref{eqn:two}A} 2+2&=f
\end{align*}
\end{document}
In other words, I'd like to provide a switch that tells an equation to display a number based on which iteration of a previous equation it is. Non-requirements:
- I can manually instruct it which equation is its ancestor; I don't need it to "figure it out" automatically.
- I also don't care what the format of these numbers is as I presume any solution will make that easy to change (so e.g. I'd be just as happy with 1.1, 1.2 instead of 1A, 1B).
- Finally, there is no need to support automatic re-labeling, as I can manually re-label the important future iterations so long as the label "grabs" the tagged-displayed number in references.
Requirement:
- The one thing that is essential is that I would like to automate the sub-numbering process so I don't risk messing it up by moving equations around / deleting them.
Unfortunately I'm not sure what this is called. Sub-referencing equations? Self-referencing equation numbering?
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at the beginning of that blank line.