Hey there, I have some trouble understanding how to find volumes and surface areas using double/triple integrals. It's not a homework or anything, just maybe you can point me into the right direction .

Here are 2 examples:

Find the surface area delimited by the surface $\displaystyle x^2+y^2=z, z \in [0,2] $

Find the volume delimited by the surface $\displaystyle x^2+y^2=z^2, z \in [0,1]$

1. I used polar coordinates here.

Shouldn't I use spherical coordinates since it has 3 variables ?(x y z).

Later Edit: I forgot the Jacobian in the first example (which is r)

2. Spherical coordinates: this i didn't got at all :-s

I'm really a newbie at this, I could really use some help :-s.