# [texhax] Re-using equation numbers

Tue Jun 15 12:44:19 CEST 2004

<quote who="Robin Fairbairns">
>> 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
>> 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:
>
> $\mathrm{\dot{H} + O_2 \rightarrow \dot{O}H + O } > \tag{\eqref{key}}$

Without AMS Math, \eqno command can replace \tag, meaning
\eqno{(\ref{key})} can accomplish the same results as above.

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