I desperately need some help with sketching cylinders and quadratic surfaces. We did this in first year and I understood it then but now that I look at it, I have no idea where to start. Oh and yes I have been in to talk with my ta quite a few times but I still dont quite understand; I'll go bother my prof tomorrow during his office hours too but for now if someone can just guide me with how to graph these monsters, I'd really appreciate it immensely. This is the only chapter I'm having trouble with. Thanks These are just some practice problems from our textbook that don't have to be handed in so if someone could give an explanation of any one of these surfaces, it would be great. I could work on the others if I understood at least one. Lol actually I think 5 is the only one that I get 1. y^2+4z^2=4 2. z=4-x^2 3. x-y^2=0 4. yz=4 5. z=cosx 6. x^2-y^2=1 So ummm yah, thanks for any help Oh and something else, I had another account here but for some reason it doesn't let me post anything anymore? Anybody know why this might be so?