# Equation relabel then reset

I have asked a previous question, but that was for cases. Here, I would like to relabel some equations midway before resetting the labelling set to default.

Code:

\documentclass[12pt]{beamer}
\usepackage{amsmath}
\usepackage{pgfpages}
\pgfpagesuselayout{resize to}[a4paper,landscape]
%\pgfpagesuselayout{2 on 1}[a4paper]
%\usetheme{Singapore}
\usepackage{bm}
%\usefonttheme[?options?]{structuresmallcapsserif}
%\definecolor{beamer@blendedblue}{RGB}{203,140,55} % changed this
\definecolor{beamer@blendedblue}{RGB}{0,102,102} % changed this
%\definecolor{beamer@blendedblue}{RGB}{0,153,153} % changed this
\usefonttheme{professionalfonts} %To get the accents aligned correctly, albeit in Computer Modern Roman
\begin{document}
%-----------------------------------------------------------------New slide ----------------------------------------------------%
\begin{frame}{Sample}
\setcounter{equation}{10}
$$F = ma$$
% Starting from here I would like 11a, 11b,...
\begin{align}
a + b &= c\\
d + e &= f
\end{align}
$$a = 1$$
% Starting from here, I would like 12, 13,..
$$f = 5$$
$$F = -kx$$
\end{frame}
\end{document}


Output:

Is there a way to freeze the current equation number n and start labeling some equations as (na) (nb)... and so on?

• Hmmmm might if you post a solution on how to do so, especially on how to freeze the current equation number? – Superman Jun 11 '20 at 21:41
• Ok, got it. But how to save the current equation number and tagging it with the letter suffix? – Superman Jun 11 '20 at 21:44
• oh you meant the current number not a literal n. I'll delete the comments – David Carlisle Jun 11 '20 at 21:46
• I was using a literal n as a description, just saying. – Superman Jun 11 '20 at 21:47
• you could use \tag{\theequation a} – David Carlisle Jun 11 '20 at 21:47

You want subequations; the label should be unique for each use of the environment.

\documentclass[12pt]{beamer}
\usepackage{amsmath}
\usepackage{pgfpages}
\pgfpagesuselayout{resize to}[a4paper,landscape]
%\pgfpagesuselayout{2 on 1}[a4paper]
%\usetheme{Singapore}
\usepackage{bm}
%\usefonttheme[?options?]{structuresmallcapsserif}
%\definecolor{beamer@blendedblue}{RGB}{203,140,55} % changed this
\definecolor{beamer@blendedblue}{RGB}{0,102,102} % changed this
%\definecolor{beamer@blendedblue}{RGB}{0,153,153} % changed this
\usefonttheme{professionalfonts} %To get the accents aligned correctly, albeit in Computer Modern Roman
\begin{document}
%-----------------------------------------------------------------New slide ----------------------------------------------------%
\begin{frame}{Sample}
\setcounter{equation}{10}
\begin{subequations}\label{freeze}
$$F = ma \tag{\ref{freeze}}$$
\begin{align}
a + b &= c\\
d + e &= f
\end{align}
$$a = 1$$
\end{subequations}
% Starting from here, I would like 12, 13,..
$$f = 5$$
$$F = -kx$$
\end{frame}
\end{document}


• Looks like a good answer! What if I have two slides and I want to apply the subequations environment on both slides with the letter suffixes on the second slide following from the previous slide? – Superman Jun 11 '20 at 22:38
• Right now, the answer applies for only one slide. How to apply it to two or more consecutive slides? – Superman Jun 11 '20 at 22:44