1

I use

\usepackage{amsmath}
\numberwithin{equation}{chapter}

It means when I make an equation. I just need to do this

\begin{equation}
    equation
\end{equation}

And it's numbered automatically.

So how can I cross-reference the equation numbered (1.2)? I don't \label it, so \ref is not helpful.

  • \ref{<equation label>}? for more, please provide minimal working example with only relevant packages. – Zarko Jan 17 '17 at 3:35
  • tyou proved only code sniped, not minimal working example :( – Zarko Jan 17 '17 at 3:46
  • Any particular reason for not wanting to use LaTeX's label-ref cross-referencing mechanism? – Mico Jan 17 '17 at 4:46
  • @Mico is this more convenient. Labeling everything is more complicated – chí trung châu Jan 17 '17 at 5:10
  • How inconvenient can it be to have to write \label{eq:second} and \ref{eq:second}? Is your paper really short? If so, just write "... as shown in equation (1.2) ..." and be done with it. I've edited the title of your posting to clarify your typesetting objective, which isn't really related to the directive \numberwithin{equation}{chapter}. – Mico Jan 17 '17 at 5:17
1
\documentclass{book}
\usepackage{amsmath}
\numberwithin{equation}{chapter}

\begin{document}
\chapter{first}
\begin{equation}\label{eq: my very first referenced equation}
    equation
\end{equation}
see \eqref{eq: my very first referenced equation} \dots
\end{document}

enter image description here

You need to run LaTeX at least twice.

Addendum: From comments to your question and changes of question follows, that you actually not interested referencing mechanism ... An alternative is using tags for numbering/tagging of equation and than referencing it manually:

\documentclass{book}
\usepackage{mathtools}% or amsmath ...

\begin{document}
\chapter{first}
\begin{equation}\tag{1.1}
    equation
\end{equation}
see (1.1) \dots
\end{document}

Result is the same as before.

0

If using \label and \ref (or \eqref) is too inconvenient for you, the leading alternative is to hard-code the cross-reference. E.g., if the equation of interest is numbered "(2.1)", you could write elsewhere

... as was shown in equation (2.1), ...

That said, you'll save yourself a lot of time and effort in the medium to long run if you learn how to use \label and \ref.

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