how can I write equation numbers in latex?

Question

how can I write equation numbers in latex. like 1, 2, and so on.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
\pdv{T^k}{t} = 
-\frac{\dot{f}_t^k}{A\varepsilon_{\textrm{cat}}C_t^k}
 \frac{T_i^k-T_i^{k-1}}{\Delta z}
+\frac{\pi D_i}{A\varepsilon_{\textrm{cat}}C_t^kC_p^k}
+\frac{\rho_{\textrm{cat}}a}{\varepsilon_{\textrm{cat}}C_t^kC_p^k}
\sum_{i=1}^{N} \eta_i^kr_i^k(-\Delta H_{\!f,i}^k)
\]
\end{document}

You don't latex does it for you. Try \begin{equation}...\end{equation} instead of \[...\]. BTW: this should be covered in any reasonable latex introduction. (BTW: I did not give this a thumb down, whoever did should have added a comment) — daleif, Jun 25 '20 at 07:30
Also, please use examples that are possible to compile in questions. This document yields an error. (BTW: I have also not given thumbs down.) — pst, Jun 25 '20 at 07:32
Do please study the posting What are the differences between $$, \[, align, equation and displaymath? — Mico, Jun 25 '20 at 10:05
Related question: math mode - Giving an equation between \[ \]'s a number - TeX - LaTeX Stack Exchange (the only difference is that the linked question the OP already know a solution and ask for a shortcut) — user202729, May 31 '23 at 13:08

score 5 · Answer 1 · answered Jun 25 '20 at 10:03

To switch from an unnumbered to a numbered displayed equation, all you have to do is replace \[ and \] with \begin{equation} and \end{equation}.

\documentclass{article}
\usepackage{amsmath,geometry}
\providecommand\pdv[2]{\frac{\partial #1}{\partial #2}}
\begin{document}
Unnumbered displayed equation:
\[
\pdv{T^k}{t} = 
-\frac{\dot{f}_t^k}{A\varepsilon_{\textrm{cat}}C_t^k}
 \frac{T_i^k-T_i^{k-1}}{\Delta z}
+\frac{\pi D_i}{A\varepsilon_{\textrm{cat}}C_t^kC_p^k}
+\frac{\rho_{\textrm{cat}}a}{\varepsilon_{\textrm{cat}}C_t^kC_p^k}
\sum_{i=1}^{N} \eta_i^kr_i^k(-\Delta H_{\!f,i}^k)
\]
\bigskip
Numbered displayed equation:
\begin{equation}
\pdv{T^k}{t} = 
-\frac{\dot{f}t^k}{A\varepsilon{\textrm{cat}}C_t^k}
 \frac{T_i^k-T_i^{k-1}}{\Delta z}
+\frac{\pi D_i}{A\varepsilon_{\textrm{cat}}C_t^kC_p^k}
+\frac{\rho_{\textrm{cat}}a}{\varepsilon_{\textrm{cat}}C_t^kC_p^k}
\sum_{i=1}^{N} \eta_i^kr_i^k(-\Delta H_{!f,i}^k)
\end{equation} 
\end{document}

score 2 · Accepted Answer · answered Jun 25 '20 at 07:59

2

In addition to the excellent suggestions above in comments section -- if you wish to do manual numbering add the \tag syntax at the end of the equation --\tag{..3.1.1a,b} \label{myeq} --the \label syntax for referencing can be plugged in if desired

Off course you can revert to auto numbering with the equation environment

And the negative points are not mine(-1)

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
{T^k}{t} = 
-\frac{\dot{f}_t^k}{A\varepsilon_{\textrm{cat}}C_t^k}
 \frac{T_i^k-T_i^{k-1}}{\Delta z}
+\frac{\pi D_i}{A\varepsilon_{\textrm{cat}}C_t^kC_p^k}
+\frac{\rho_{\textrm{cat}}a}{\varepsilon_{\textrm{cat}}C_t^kC_p^k}
\sum_{i=1}^{N} \eta_i^kr_i^k(-\Delta H_{\!f,i}^k) \tag{..3.1.1a,b} \label{myeq}
\]
For example, see \eqref{myeq}.
\end{document}

answered Jun 25 '20 at 07:59

js bibra

21,280

4

I think it should be labelled quite strongly that for newcomers this is not a good idea. Let LaTeX handle the numbering. Otherwise we'll see users writing \tag{1} , \tag{2} .... – daleif Jun 25 '20 at 08:07
1

Observe that the OP asked about simple equation numbers such as 1 and 2, not ..3.1.1a,b. – Mico Jun 25 '20 at 10:08
I just had need non-default equation numbers so this answer worked well for me. – John1024 Oct 07 '20 at 21:47

score 0 · Answer 3 · answered Jun 25 '20 at 16:06

Either you can continue to use \[ \] and use the \tag{} to label the equation as well as the '\label{}' to allow it to be referenced later, or you can use '\begin{equation}' & '\end{equation}' instead so that it will automatically label the equation for you.

If you choose to use \begin{equation} and you would like your equation to be numbered differently, you can still use \tag to label it differently.

For example:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
\pdv{T^k}{t} = 
-\frac{\dot{f}_t^k}{A\varepsilon_{\textrm{cat}}C_t^k}
 \frac{T_i^k-T_i^{k-1}}{\Delta z}
+\frac{\pi D_i}{A\varepsilon_{\textrm{cat}}C_t^kC_p^k}
+\frac{\rho_{\textrm{cat}}a}{\varepsilon_{\textrm{cat}}C_t^kC_p^k}
\sum_{i=1}^{N} \eta_i^kr_i^k(-\Delta H_{\!f,i}^k) \tag{1.1} \label{eq1}
\]
\end{document}

or,

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\pdv{T^k}{t} = 
-\frac{\dot{f}_t^k}{A\varepsilon_{\textrm{cat}}C_t^k}
 \frac{T_i^k-T_i^{k-1}}{\Delta z}
+\frac{\pi D_i}{A\varepsilon_{\textrm{cat}}C_t^kC_p^k}
+\frac{\rho_{\textrm{cat}}a}{\varepsilon_{\textrm{cat}}C_t^kC_p^k}
\sum_{i=1}^{N} \eta_i^kr_i^k(-\Delta H_{\!f,i}^k) \tag{1.1} \label{eq1}
\end{equation}
\end{document}

how can I write equation numbers in latex?

3 Answers3