Results 1 to 3 of 3

Math Help - Find the Indefinite Integral part b

  1. #1
    Junior Member
    Joined
    Feb 2010
    Posts
    52

    Find the Indefinite Integral part b

    Hi again,
    Im studying for a exam tomorrow and have another question for this forum =)


    ⌡ e^(-x) sec^2(e^(-x)) dx

    For this problem I approached it by substituting sec^2(e^(-x)) w/ u^2 => I then got stuck w/ (sec^3(e^(-x))/3 * 1/(sec(e^(-x))*tan(e^(-x))) + C

    The answer key just gives -tan(e(-x)) + C

    Please help
    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 ugkwan View Post
    Hi again,
    Im studying for a exam tomorrow and have another question for this forum =)


    ⌡ e^(-x) sec^2(e^(-x)) dx

    For this problem I approached it by substituting sec^2(e^(-x)) w/ u^2 => I then got stuck w/ (sec^3(e^(-x))/3 * 1/(sec(e^(-x))*tan(e^(-x))) + C

    The answer key just gives -tan(e(-x)) + C

    Please help
    Substitute u = e^{-x}.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,579
    Thanks
    1418
    Generally speaking, it is not a good idea to try very complicated substitutions "all at once". It would be better to do as mr. fantastic suggests: let u= e^{-x} so that du= -e^{-x}dx and the problem becomes -\int  sec^2(u)du. Then, perhaps, use another substitution if you found it helpful.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Find the indefinite integral
    Posted in the Calculus Forum
    Replies: 4
    Last Post: November 15th 2010, 03:20 AM
  2. Find the indefinite integral
    Posted in the Calculus Forum
    Replies: 3
    Last Post: September 25th 2010, 12:24 PM
  3. Find the Indefinite Integral (cosx/1-cos^2x)dx
    Posted in the Calculus Forum
    Replies: 12
    Last Post: June 29th 2008, 11:59 AM
  4. Part of an Indefinite Integral Problem
    Posted in the Calculus Forum
    Replies: 3
    Last Post: March 16th 2008, 09:29 PM
  5. find the indefinite integral
    Posted in the Calculus Forum
    Replies: 2
    Last Post: February 15th 2007, 06:03 AM

Search Tags


/mathhelpforum @mathhelpforum