Reuse a previous equation with the original numbering

Question

Here I am stuck again!

I have this equation 4.42 but I need to display this same equation, with this original number (4.42), in chapter 6. How can I do that?

The equation is:

\begin{equation} \label{Po}
    \Pi=\pi-\frac{1}{3}c_s k_B T \phi \textbf{F}^2
\end{equation}

And below you can see the equation in chapter 4.

How to put this equation in chapter 6, but enumerated 4.42?

\begin{equation} \label{Po} \Pi=\pi-\frac{1}{3}c_s k_B T \phi \textbf{F}^2 \tag{\ref{<equation 4.42 label>}} \end{equation} ? in preamble should be loaded package amsmath . — Zarko, Nov 27 '17 at 20:29

score 1 · Answer 1 · answered Nov 27 '17 at 20:30

1

For example, \label and \ref can be used:

\documentclass{report}
\usepackage{amsmath}
\begin{document}
Chapter 4
\setcounter{chapter}{4}
\setcounter{equation}{41}

\begin{equation} \label{Po}
    \Pi=\pi-\frac{1}{3}c_s k_B T \phi \textbf{F}^2
\end{equation}

Chapter 6
\setcounter{chapter}{6}

\begin{equation} \tag{\ref{Po}}
    \Pi=\pi-\frac{1}{3}c_s k_B T \phi \textbf{F}^2
\end{equation}

\end{document}

answered Nov 27 '17 at 20:30

Heiko Oberdiek

271,626

Many thanks for helping me. That solved my problem. Have a nice week! – Ingrid Nov 27 '17 at 20:37
And you beat me by 15 seconds -;). – AboAmmar Nov 27 '17 at 20:37

score 1 · Answer 2 · answered Nov 27 '17 at 20:31

Add \tag{<ref. to original eq.>} to the equation in chapter 6 with reference to the original equation in chapter 4.

\documentclass[a4paper]{article}
\usepackage{amsmath}
\begin{document}

\begin{equation}\label{eq:one}
    \begin{split}
        A  = & \left( a + B + \right . \\
             & \left.{} + c + d \right)
    \end{split}
\end{equation}

\begin{equation} \label{repeated}\tag{\ref{eq:one}}
    \Pi=\pi-\frac{1}{3}c_s k_B T \phi \textbf{F}^2
\end{equation}

\begin{equation} \label{Po}
    \Pi=\pi-\frac{1}{3}c_s k_B T \phi \textbf{F}^2
\end{equation}    

\end{document}

Thanks for your reply. I needed what Heiko Oberdiek did below. Have a nice week! — Ingrid, Nov 27 '17 at 20:37

Reuse a previous equation with the original numbering

2 Answers2