WYSIWYG, TinyMCE and DruTeX issue

Hi everybody.
On my website I installed WYSIWYG API, and TinyMCE that are working properly.
I also installed DruTeX and configured it so that it works properly as well.

The problem arise when I try to use tinyMCE as default editor for a post with DruTeX input format.

If I use for example $x^2$ Drutex renders the latex expression and I can see "x square" png in my page.

The problem is if I try to insert a formula using x^2

The first time I save (or I make a preview), I get the correct png with the formula.

But the "equation" tag are removed from the page I writing, so that each time I want to
preview it I have to rewrite all the and I need.

I guess this is a tinyMCE issue (when using richtext).
I was just wondering if there is a way to configure it so that when it enconters and
they are not removed from my page.

I would be very gratefull if you could give me any advice!!!
(I'm very new to Drupal, this is my fourth or fifth day of web administration... I don't really
have a clue where to start on :))

Thank you very much in advance,
Cheers