Why is it written “LaTeX” and not “latex”? A good question. Here is an answer. But from here on we’ll just write “latex”.
Do I have to use latex?
Short answer = No.
Slightly longer answer = No, but your homework has to be typeset.
Even longer answer = No, but your homework has to be typeset, and:
We strongly recommend that you use latex.
Though it is difficult initially, it is by far the easiest method for producing legible mathematical documents.
You might try using various word processors (word, libreoffice, openoffice, etc) but we take no responsibility for the pain, suffering and hair loss it might cause.
There are more wysiwyg (or wysiwym) solutions like texmacs and LyX.
Another possibility is to use mathml or mathjax to embed your mathematics in a webpage for printing. You could also try to use markdown with some extensions to typeset mathematics. These might not be so easy to do.
Final answer = We do not mind what you use, as long as the homework you hand in is neatly typeset and easy to read and printed on paper and stapled.