I am doing a physics project report. I want to write a system of multiple equations and nominate them as if they were subequations. I need to label them separately to make references to them later, like the following :
\documentclass{article}
\usepackage[french]{babel}
\usepackage[utf8]{inputenc}
\usepackage{amsmath,amssymb}
\begin{document}
\begin{subequations} \label{syst3d}
\begin{gather}
\partial_t \Delta v_z - \mathcal{P}(\Delta^2 v_z + \Delta_\mathrm{h}\theta) = 0 \label{syst3d1} \\
\partial_t \theta = \Delta \theta + \mathcal{R} v_z \label{syst3d2}
\end{gather}
\end{subequations}
\end{document}
If I do that, I have indeed the two equations labelled 1.a and 1.b. But there are not aligned and there is not a bracket { . So I did some research and I found a code like this :
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{cases}
\partial_t \Delta v_z - \mathcal{P}(\Delta^2 v_z + \Delta_\mathrm{h}\theta) = 0 \\
\partial_t \theta = \Delta \theta + \mathcal{R} v_z\\
\end{cases}
\end{equation}
\end{document}
In this I have indeed the { but not a nomination like in subequations, just a (1) for all the system. I also can't label them, there is a package error "multiple labels". I tried to replace "\begin{equation}" by a "\begin{subequations}" but the nomination disappears and there is an error "missing $ inserted"... I hope it is not a question already asked by someone. If there is, may you give me the link because I didn't find it ?
