Results 1 to 2 of 2

Math Help - Help finding surface area of a surface

  1. #1
    Newbie
    Joined
    Aug 2008
    Posts
    20

    Help finding surface area of a surface

    Suppose the curve defined by y=4x^(1/2) for x <= x <= 1 is revolved about the x-axis.

    1.) Find the surface area of the surface.

    My answer:
    b
    S= 2PI ∫ r(x) [sqrt of 1 + (f'x)]^2
    a
    1
    =2PI∫ 4x^1/2 [sqrt of 1 + 2x^3/2]^2
    0

    1
    =2PI/6∫ 6(4x^1/2)(1+2x^3)^1/2
    0

    1
    =2PI/6∫6(4x^1/2)(1+2x^3)^1/2
    0

    1
    =PI/3[((1+2x^3)^3/2)/(3/2)|
    0

    =PI/4.5[((3^3/2)-1)]

    My answer=4.19PI/4.5

    Have I come anywhere close to doing this problem correctly? I'm thinking I might have done something wrong. If I have, can someone show me what I did wrong or how to do this problem correctly? Thanks
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,888
    Thanks
    682
    y = 4\sqrt{x}

    y' = \frac{2}{\sqrt{x}}

    (y')^2 = \frac{4}{x}


    S = 2\pi \int_0^1 4\sqrt{x} \cdot \sqrt{1 + \frac{4}{x}} \, dx

    S = 8\pi \int_0^1 \sqrt{x + 4} \, dx

    can you finish?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Need help finding surface area
    Posted in the Geometry Forum
    Replies: 4
    Last Post: March 6th 2012, 10:58 AM
  2. [SOLVED] Finding the Surface Area of the curve?
    Posted in the Calculus Forum
    Replies: 5
    Last Post: July 26th 2010, 01:34 AM
  3. Finding the surface area of a function
    Posted in the Calculus Forum
    Replies: 3
    Last Post: March 25th 2010, 06:12 PM
  4. finding the lateral surface area
    Posted in the Calculus Forum
    Replies: 1
    Last Post: March 6th 2010, 02:12 PM
  5. Volume, Surface Area, and Lateral Surface Area
    Posted in the Geometry Forum
    Replies: 1
    Last Post: April 14th 2008, 11:40 PM

Search Tags


/mathhelpforum @mathhelpforum