Add a referencable latex align equation

[gavinhesketh]

Description

Hi, I'd like to add some aligned equations to a document compiled as html and pdf.
For example, I can include aligned equations in my .qmd file like this:

\begin{align*}
(\gamma^\mu p_\mu -m)u&=0\\
(\gamma^\mu p_\mu -m)u&=0
\end{align*}

which compiles and displays correctly for pdf and html, but I can't work out how to make this referenceable in the document. eg this works for equations:

see  @eq-MomDE
$$
(\gamma^\mu p_\mu -m)u=0
$${#eq-MomDE}

but similar syntax does not work for align. I find this works for the html output:

See  @eq-MDE
$$
\begin{align*}
(\gamma^\mu p_\mu -m)u&=0\\
(\gamma^\mu p_\mu -m)u&=0
\end{align*}
$${#eq-MDE}

... but not for pdf as the .tex file has "erroneous nesting of equation structures":

\begin{equation}\phantomsection\label{eq-MDE}{
\begin{align*}
(\gamma^\mu p_\mu -m)u&=0\\
(\gamma^\mu p_\mu -m)u&=0
\end{align*}
}\end{equation}

Is there a way to refer to an align that works for pdf and html? Thanks!

[mcanouil]

Please use the search before opening new threads, this has been discussed extensively in several places already:

• https://github.com/quarto-dev/quarto-cli/issues?q=is%3Aissue%20state%3Aopen%20label%3Amath

• https://github.com/quarto-dev/quarto-cli/discussions?discussions_q=is%3Aopen+label%3Amath

• Use \tag{} info for eq cross referencing in the HTML book output #310

• referencing equations inside $$ \begin{align} environment #2275