The draeing toolbar in Powerpoint isn't too bad, you can draw the vector, right-click on it to look at the prpoerties then scale & rotate as you need to do to finish the assignment. Latex will work, but you will have to get thru the learning curve.
Okay thanks, I'm doing my assignment in LaTeX anyhow so I'd prefer using that to draw too, but I can't find anything on drawing coordinate systems / vectors in LaTeX, got any links?
There are a number of drawing systems for LaTeX, all of which can do what you ask. My personal favorite is http://www.ctan.org/tex-archive/help/Catalogue/entries/pgf.html, but Asymptote and Metapost seem like reasonable alternatives. pgf/Tikz can be used inline in a LaTeX document. Its default length unit is centimeters, the origin is in the lower left corner, and the drawing area expands automatically to fit its contents.