How to convert z(x+y) to cylindrical?

Question

From what I currently know for converting rectangular to cylindrical:

$r = \sqrt{x^2+y^2}$ ---OR---> $r^2 = x^2+y^2$

$\theta = tan^{-1}(y/x)$

$z = z$

I'm trying to convert, $z(x+y)$, for doing my triple integral in cylindrical coordinates.

I can't think of how to go about converting the x+y portion

Answer 1

$x=r\cos \theta$

$y=r\sin \theta$