## LaTeX forum ⇒ Math & Science ⇒ How to number equations in cases. Topic is solved

Information and discussion about LaTeX's math and science related features (e.g. formulas, graphs).
keepitcool
Posts: 2
Joined: Sat Feb 13, 2016 7:42 pm

### How to number equations in cases.

Hello!

I have written the following:
$\begin{cases}\frac{1}{ T(t)} \partial_{tt} T(t) = - \lambda^2, \\\\c^2 \frac{1}{R(r)} \partial_{rr} R(r) + \frac{1}{R(r)} \frac{1}{r} \partial_{r} R(r) + \frac{1}{r^2} \partial_{\theta \theta} \frac{1}{\Theta ( \theta) } \Theta( \theta ) = - \lambda^2. \label{eq:sep_var2} \\\end{cases}$

I wanted each equation to have a number to ref them later on, but I don't know how to number them.

Best regards

Stefan Kottwitz
Posts: 9593
Joined: Mon Mar 10, 2008 9:44 pm
Welcome to the forum!

A cases environment is usually part of a formula structure such as an equation. Equations can be numbered.

\documentclass{article}\usepackage{amsmath}\begin{document}\begin{equation}   \begin{cases}   \frac{1}{ T(t)} \partial_{tt} T(t) = - \lambda^2,  \\     \\     c^2  \frac{1}{R(r)} \partial_{rr} R(r) + \frac{1}{R(r)} \frac{1}{r}     \partial_{r} R(r) + \frac{1}{r^2} \partial_{\theta \theta} \frac{1}{\Theta     ( \theta) } \Theta( \theta ) = - \lambda^2. \label{eq:sep_var2} \\   \end{cases}\end{equation}\end{document}

Stefan

Stefan Kottwitz
Posts: 9593
Joined: Mon Mar 10, 2008 9:44 pm
For the case that you would like to have each line within that cases environment numbered: you could use the cases package:

\documentclass{article}\usepackage{cases}\begin{document}\begin{numcases}{}   \frac{1}{ T(t)} \partial_{tt} T(t) = - \lambda^2,  \\     c^2  \frac{1}{R(r)} \partial_{rr} R(r) + \frac{1}{R(r)} \frac{1}{r}     \partial_{r} R(r) + \frac{1}{r^2} \partial_{\theta \theta} \frac{1}{\Theta     ( \theta) } \Theta( \theta ) = - \lambda^2. \label{eq:sep_var2}\end{numcases}\end{document}

Stefan