Why doesn't Jupyter notebook print the mathematical symbol input in markdown?

On Coursera (algorithms course from CU), I tried to input theta in the Jupyter notebook in Coursera but it doesn't show the symbol when I click the save icon (floppy disk icon)

 $\theta (n X k-1 + ...) = $\theta (n*k^2)

I expected to see the mathematical symbol. When is the markdown script interpreted again?

Update: On my local Jupyter in VS Code, I see

So the second theta symbol is not showing

Wouldn't you use the following?:

 $\theta (n X k-1 + ...) = \theta (n*k^2)$

The $ signals the start of the inline LaTeX and a second $ is used to end it

Looking at the result of the following rendered in Jupyter markdown may give you a better idea.

This is before inline LaTeX. $\theta (n X k-1 + ...) = \theta (n*k^2)$ This is after inline LaTeX.

For more information, see under 'Inline Typesetting (Mixing Markdown and TeX)' here in the Jupyter Notebook Documentation.

If you want the formula centered in the middle of page:

This is before centered LaTeX. $$\theta (n X k-1 + ...) = \theta (n*k^2)$$ This is after centered LaTeX.

Note there the starting signal is double dollar sign. And then it is ended with other instance of double dollar sign.

See the bottom of here under 'Other Syntax' here in the Jupyter Notebook Documentation.