1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Area of a smooth surface

  1. Jan 13, 2014 #1
    Here's my work: http://i.imgur.com/UMj72Ub.png

    I used the surface area differential for a parametrized surface to solve for the area of that paraboloid surface. My friend tried solving this by parametrizing with x and y instead of r and theta which gave him the same answer. I would greatly appreciate it if anyone else can verify if this answer is correct as it looks out of the ordinary.


  2. jcsd
  3. Jan 13, 2014 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    You've a few typos in there, but it is essentially right.
    Some spurious 'r' factors in rr. You don't want the modulus signs around the first mention of rr x rθ.
    You should mention the reasoning behind writing z = r2 instead of z = 4-r2.
  4. Jan 13, 2014 #3
    Sorry about the part where I wrote z = r2. I essentially set z = 0 and moved the 4 over and got -4 = -x2-y2. Eliminate the negatives and I ended up with 4 = x2+y2 where r = 2. Hence why I set z = r2.

    Thanks again!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted