# [texhax] Re-using equation numbers

Robin Fairbairns Robin.Fairbairns at cl.cam.ac.uk
Tue Jun 15 12:30:49 CEST 2004

> The following is a numbered equation in an early chapter of a thesis
>
> \mathrm{\dot{H} + O_2  \rightarrow  \dot{O}H + O }
> \label{key}
>
>
> We want to re-use the equation number in a restatement of the
> equation  many pages on from the first statement because the reader
> may well have forgotten what it referred to ...
>
> Is there a better or more elegant solution than this?
>
> $$> \mathrm{\dot{H} + O_2 \rightarrow \dot{O}H + O } \rule{25pt}{0pt} > \eqref{key} >$$
>
> in LaTeX + Amsmath

don't use  in amsmath; use the amsmath \tag command:

$\mathrm{\dot{H} + O_2 \rightarrow \dot{O}H + O } \tag{\eqref{key}}$

robin