Results 1 to 5 of 5

Thread: Sketching the Graph of an Interval (Help Please)

  1. #1
    Newbie
    Joined
    Nov 2007
    Posts
    10

    Sketching the Graph of an Interval (Help Please)

    Given first sketch the graph y = f(x) on the given interval.
    Then find the integral of
    f using your knowledge of area formulas for

    rectangles, triangles and circles.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor kalagota's Avatar
    Joined
    Oct 2007
    From
    Taguig City, Philippines
    Posts
    1,026
    Quote Originally Posted by evansf View Post
    Given first sketch the graph y = f(x) on the given interval.

    Then find the integral of
    f using your knowledge of area formulas for
    rectangles, triangles and circles.

    \int_{-2}^4 |3 - |3x||dx = \int_{-2}^4 |3 - 3|x||dx = \int_{-2}^4 3|1 - |x||dx.. now, this can be separated to

    \int_{-2}^4 |3 - |3x||dx = ... = \int_{-2}^0 3|1 - |x||dx + \int_{0}^4 3|1 - |x||dx..

    we know, in the first addend, x is negative, hence we take |x| = -x; on the other hand, in the second addend, x is positive hence |x| = x

    so the integral would be

    \int_{-2}^0 3|1 - |x||dx + \int_{0}^4 3|1 - |x||dx = \int_{-2}^0 3|1 + x|dx + \int_{0}^4 3|1 - x|dx

    now, we have to check where |1-x| is positive or negative and |1+x| is positive or negative..


    for |1-x|, we take 1-x if 1-x >= 0 or x <= 1; we take x-1 otherwise

    for |1+x|, we take 1+x if 1+x >= 0 or x >= -1; we take -x-1 otherwise

    so now,

    ... = \int_{-2}^{-1} 3(-1 - x)dx + \int_{-1}^{0} 3(1 + x)dx + \int_{0}^1 3(1 - x)dx + \int_{1}^4 3(x - 1)dx

    so can you do it now??
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Nov 2007
    Posts
    10

    How do you integrate it?

    ...
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor kalagota's Avatar
    Joined
    Oct 2007
    From
    Taguig City, Philippines
    Posts
    1,026
    they are just linear functions, then they can easily be integrated.. Ü
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Moderator
    topsquark's Avatar
    Joined
    Jan 2006
    From
    Wellsville, NY
    Posts
    9,079
    Thanks
    152
    Awards
    1
    Quote Originally Posted by evansf View Post
    ...
    You might try posting a message in the message box, rather than just in the title.

    Take a look at your graph. The integral is the total area between the function and the x axis. (Areas under the x axis count as negative.) As your function is composed of sections of straight lines, your areas are triangles. Easy to find the area of these.

    -Dan
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Sketching graph in R3
    Posted in the Calculus Forum
    Replies: 2
    Last Post: December 16th 2010, 04:08 AM
  2. graph sketching qn
    Posted in the Calculus Forum
    Replies: 7
    Last Post: September 12th 2010, 06:05 AM
  3. Graph sketching
    Posted in the Algebra Forum
    Replies: 4
    Last Post: June 18th 2009, 06:08 AM
  4. Replies: 2
    Last Post: May 5th 2009, 11:23 AM
  5. Need help sketching a graph
    Posted in the Calculus Forum
    Replies: 1
    Last Post: October 22nd 2007, 01:14 PM

Search Tags


/mathhelpforum @mathhelpforum