Results 1 to 5 of 5

Math Help - inflection points

  1. #1
    Newbie
    Joined
    Jul 2008
    Posts
    16

    inflection points

    f(x)=x+sinx [0,2pi]
    f'(x)=1 +cosx
    f''(x)= -sinx
    0=-sinx
    x= 0, pi and 2pi
    i dont know if i can call 0 and 2pi inflection points since they are end points of the closed interval....
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by zintore View Post
    f(x)=x+sinx [0,2pi]
    f'(x)=1 +cosx
    f''(x)= -sinx
    0=-sinx
    x= 0, pi and 2pi
    i dont know if i can call 0 and 2pi inflection points since they are end points of the closed interval....
    Critical points are found by solving f'(x) = 0, NOT f''(x) = 0.

    Note also, that a point has coordinates, that is, an x-coordinate AND a y-coordinate.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Jul 2008
    Posts
    16

    sorrry still not answered

    but i was asking for the inflection points, where the graph changes concavity. can i say it changes concavity at an end point??
    Last edited by zintore; July 27th 2008 at 09:49 PM. Reason: still not answered!
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    Joined
    Aug 2007
    From
    USA
    Posts
    3,111
    Thanks
    2
    1) The derivative does not exist at an endpoint.

    2) Nothing can "change" at an endpoint, since there is only one side.

    3) Extrema can occur at endpoints, but the calculus will find them only by design or coincidence. You must check the endpoints yourself.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Member
    Joined
    Apr 2008
    From
    Seoul, South Korea
    Posts
    128
    i thought by definition inflection points are where f''(x)=0. is that not true?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 3
    Last Post: August 24th 2011, 12:35 PM
  2. Replies: 16
    Last Post: June 10th 2011, 07:49 AM
  3. Replies: 1
    Last Post: April 20th 2010, 08:36 PM
  4. Replies: 2
    Last Post: October 29th 2009, 09:02 PM
  5. Replies: 5
    Last Post: February 27th 2009, 08:48 PM

Search Tags


/mathhelpforum @mathhelpforum