I am participating in the IYMC and need to type some answers. As a member of this site for $9$ months, I find myself much more comfortable typing in MathJax than in Microsoft Word. So I hope that I can simply type in what I need in the body and use the screenshots to create a pdf file with my answers. I will not be posting the question, only use the display screen below it. So I was wondering if it was a copyright infringement and if I should mention where I typed the answers. Thank you for your patience.
That said, there are better solutions that allow you to also save the files and edit them again later (something you cannot do with a screenshot). StackEdit 4 is one such: as the name suggests, it is a web based editor very similar to what we use here. (StackEdit 5 diverged from it by switching from MathJaX to KaTeX.)