Hey, I am really rusty on my multivariable calc stuff and cannot seem to get the right answer to...

$\displaystyle f(x,y,z)=\tan^{-1}(\frac{1}{xy^{2}z^{3}})$ with respect to x and with respect to y.

Help? I don't know what techniques to imply. I just went ahead and did it as if it were just a single variable function since I only needed it with respect to x and also with respect to y.

Thanks