My professor assigned this problem:

F(x,y) = x / y^2. We had to find the Unit Tangent Vector at the point (2, -2).

I honestly didn't know where to even start with this. I know what to do if I'm given a vector function, but F(x,y) sure isn't one.

I'm just looking for pointers on how to start, after that I should be able to do it on my own.