Results 1 to 7 of 7

Math Help - integrate to find area

  1. #1
    Junior Member
    Joined
    Sep 2008
    From
    houston
    Posts
    25

    integrate to find area

    i am doing area between curves. now i im on like the third step. i did the top minus bottom and now my integral is this.

    integral going from 1 to 5 (1/x^2) dx...

    now the next step i see is that that equals [-1/x]with integral 1 to 5. how do i get from the first integral to the second?

    thx
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Mar 2010
    From
    Florida
    Posts
    3,093
    Thanks
    5
    I am not sure with what you are getting at. Can you just post the question from the book?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Sep 2008
    From
    houston
    Posts
    25
    okay it says sketch the region bounded by the graphs of the equasions, and determien the area of the region.

    the problem is y=1/x^2, y=0, x=1, x=5.

    so that means the integrals are going from 1 to 5. i know how to sketch the graph. and then so i got

    integral from 1 to 5 (1/x^2) dx because there are vertical slices. not sure how to integrate after that to find the area. lol sorry if im being confusing.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor harish21's Avatar
    Joined
    Feb 2010
    From
    Dirty South
    Posts
    1,036
    Thanks
    10
    Quote Originally Posted by FinalFantasy9291 View Post
    i am doing area between curves. now i im on like the third step. i did the top minus bottom and now my integral is this.

    integral going from 1 to 5 (1/x^2) dx...

    now the next step i see is that that equals [-1/x]with integral 1 to 5. how do i get from the first integral to the second?

    thx

    \int_1^5 \frac{1}{x^2} dx = [\frac{x^{-2+1}}{-2+1}]_1^5 = [\frac{-1}{x}]_1^5 = [\frac{-1}{5} - \frac{-1}{1}] = \frac{-1}{5} + 1 = \frac{4}{5}
    Follow Math Help Forum on Facebook and Google+

  5. #5
    MHF Contributor
    Joined
    Mar 2010
    From
    Florida
    Posts
    3,093
    Thanks
    5
    Integrate like you normal would. Look above harish21 did it.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Junior Member
    Joined
    Sep 2008
    From
    houston
    Posts
    25
    this is probably a really stupid question but how did you get -1/x.

    i like ur sig btw.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    MHF Contributor harish21's Avatar
    Joined
    Feb 2010
    From
    Dirty South
    Posts
    1,036
    Thanks
    10
    Quote Originally Posted by FinalFantasy9291 View Post
    this is probably a really stupid question but how did you get -1/x.

    i like ur sig btw.
    You need to have a good look at your book and learn the basic integration skills.

    \int \frac{1}{x^2} dx = \int x^{-2} dx= \frac{x^{-2+1}}{-2+1} = \frac{x^{-1}}{-1} = - {x^{-1}} = \frac{-1}{x}
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: November 1st 2010, 02:30 PM
  2. Replies: 2
    Last Post: February 1st 2010, 05:22 AM
  3. Integrate - Area Under the Curve
    Posted in the Calculus Forum
    Replies: 7
    Last Post: November 13th 2008, 01:05 PM
  4. integrate to find volume
    Posted in the Math Topics Forum
    Replies: 2
    Last Post: April 5th 2008, 08:52 PM
  5. find area of shaded area (yellow)
    Posted in the Geometry Forum
    Replies: 8
    Last Post: September 4th 2007, 08:34 AM

Search Tags


/mathhelpforum @mathhelpforum