Update writing-mathematical-expressions.md: Unsupported Math Blocks in <details> Blocks

[alernety]

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This issue is about displaying math blocks inside of the details blocks (and potentially other HTML blocks) regardless of the type of math block. This can include blocks such as

$$
\begin{pmatrix}
  0 & 1 \\
  2 & 3
\end{pmatrix}
$$

or blocks written like this:

```math
\begin{pmatrix}
  0 & 1 \\
  2 & 3
\end{pmatrix}
```

This issue is currently blocking the use of math blocks inside of details blocks, as well as other HTML blocks. This limitation prevents users from taking full advantage of these blocks, and should be noted in documentation. To ensure users are not held back, we must actively search for a potential solution to this issue so that math blocks can be displayed in these blocks.

Why:

Closes ISSUE

What's being changed (if available, include any code snippets, screenshots, or gifs):

Check off the following:

• [x] I have reviewed my changes in staging (look for the "Automatically generated comment" and click the links in the "Preview" column to view your latest changes).
• [x] For content changes, I have completed the self-review checklist.

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[github-actions[bot]]

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The table contains an overview of files in the content directory that have been changed in this pull request. It's provided to make it easy to review your changes on the staging site. Please note that changes to the data directory will not show up in this table.

---

Content directory changes

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Source	Preview	Production	What Changed
get-started/writing-on-github/working-with-advanced-formatting/writing-mathematical-expressions.md	fpt ghec ghes@ 3.7 3.6	fpt ghec ghes@ 3.7 3.6

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fpt: Free, Pro, Team ghec: GitHub Enterprise Cloud ghes: GitHub Enterprise Server ghae: GitHub AE

[shango420]

This issue is about displaying math blocks inside of the details blocks (and potentially other HTML blocks) regardless of the type of math block. This can include blocks such as

$$
\begin{pmatrix}
  0 & 1 \\
  2 & 3
\end{pmatrix}
$$

or blocks written like this:

```math
\begin{pmatrix}
  0 & 1 \\
  2 & 3
\end{pmatrix}
```

This issue is currently blocking the use of math blocks inside of details blocks, as well as other HTML blocks. This limitation prevents users from taking full advantage of these blocks, and should be noted in documentation. To ensure users are not held back, we must actively search for a potential solution to this issue so that math blocks can be displayed in these blocks.

Why:

Closes ISSUE

What's being changed (if available, include any code snippets, screenshots, or gifs):

Check off the following:

• [x] I have reviewed my changes in staging (look for the "Automatically generated comment" and click the links in the "Preview" column to view your latest changes).
• [ ] For content changes, I have completed the self-review checklist.

[cmwilson21]

@ALernety Thanks so much for opening a PR! I'll get this triaged for review :zap:

[isaacmbrown]

Hi @ALernety, thanks for the PR! It appears to me that matrices render correctly IF you include a line of whitespace after the HTML tag.

For example,

<details>
<summary>Matrix</summary>

```math
\begin{pmatrix}
  0 & 1 \\
  2 & 3
\end{pmatrix}
```

</details>

Appears to render correctly:

Matrix

\begin{pmatrix}
  0 & 1 \\
  2 & 3
\end{pmatrix}

I wonder if you could check whether this works for your use case too, and update your PR to reflect this if so? ✨

[cmwilson21]

It doesn't look like any updates have been on this for a while, so I'm going to go ahead and close it out 💛

Feel free to ping me here to reopen if it continues to be an issue.