At some point it was possible but a bit broken. I remember there was a talk about it back then - since then I use a solution of using some LaTeX to image service.

I've often used this one: https://latex.codecogs.com/gif.latex?y=sin(x)

As I'm not sure new website will show this as image, the code is:

https://latex.codecogs.com/gif.latex?y=sin(x)

It is, but it doesn't work as well as it should. You can try to input the formula using this toolbar button:

Hopefully LaTeX support will be better when we change editors (very soon).

Update: with the recent editor change LaTeX can be added directly in the post.

You can also use the Math Preview feature. If you have LaTeX in the editor and click on it, you'll see a preview of the resulting math as it will be displayed when posted.