This is MathJax with custom open/close tags (`$`

instead of `\(`

).

Anki uses `\(`

and `\)`

for inline equations, and `\[`

and `\]`

for display equations.

https://docs.ankiweb.net/#/math?id=mathjax

It probably won’t affect this deck, but in general

Please avoid changing the standard open/close tags (`\(`

and `\[`

), as Anki expects them to look like that.

https://anki.tenderapp.com/kb/card-appearance/customizing-mathjax

The card template is a bit old and contains a dinamycally loaded MathJax 2 library that break recent Anki builds with a built-in MathJax 3 support.

```
Uncaught (in promise) TypeError: Cannot read property 'promise' of undefined
at reviewer.js:46
43 .then(() => _runHook(onUpdateHook))
44 .then(() =>
45 // @ts-ignore wait for mathjax to ready
46 MathJax.startup.promise.then(() => {
47 // @ts-ignore clear MathJax buffer
48 MathJax.typesetClear();
49 // @ts-ignore typeset
50 return MathJax.typesetPromise(qa.slice(0, 1));
51 }))
52 // and reveal when processing is done
53 .then(() => new Promise((resolve) => qa.fadeTo(fadeTime, 1, () => resolve())))
54 .then(() => _runHook(onShownHook))
```

To fix it, there’s no need to dynamically load MathJax 2 anymore, but it’s necessary to convert configuration for MathJax 2 to MathJax 3.

In short, click the `Cards...`

button and replace the Front Template with the following code.

```
{{Front}}
<script>
MathJax.config.tex.inlineMath = [['$','$']];
MathJax.config.tex.displayMath = [['$$','$$']];
MathJax.startup.getComponents();
</script>
```

There might be no difference in the preview screen, it might be still blank, but once you close the card template window and open it again or go back to the main window, everything should be fixed.