# Equation numbering with subscripts

Could anyone tell me, how can I obtain an equation numbering as displayed in the textsample? I am talking about (4.1)_\pm.

• Welcome to TeX.SE! \tag{} is what you need. Btw, please add a source you take the screenshot from. – user156344 Feb 28 at 14:15
• Thank you, I already tried, but unfortunately \tag{} is not producing the desired result. It Looks like ((1)_-). Moreover, I would prefer a solution where the equation-number is determinier by Latex and not by myself, as I will need to refer to these equations later. – E.ElBehi Feb 28 at 14:28
• Please, the name is “Ennio De Giorgi”, with a space. Writing it “DeGiorgi”, US style, is wrong. – egreg Feb 28 at 14:46
• Sorry, the extract is not my work. And besides DeGiorgi-function classes are written like this, throughout the literature. Besides, this is not the topic here – E.ElBehi Feb 28 at 14:56

Try:

\documentclass[12pt]{article}
\usepackage[a4paper]{geometry}
\usepackage{amsmath}
\numberwithin{equation}{section}

\begin{document}
\section{First}
$$a = b \tag*{(\theequation)_{\pm}}\refstepcounter{equation}$$
$$c = d \tag*{(\theequation)_{-}}\refstepcounter{equation}$$
\end{document}


• @Mico Agreed. My answer was just a quick and dirty trick to add section numbers to equation number while using article. – Denis Mar 1 at 12:47
• @Denis - I've taken the liberty of editing your code to modify the way the composite "numbering" of equations is performed. – Mico Mar 1 at 13:40