Results 1 to 3 of 3

Math Help - Another integral

  1. #1
    Member
    Joined
    Jul 2005
    Posts
    187

    Another integral

    another problem
    Attached Thumbnails Attached Thumbnails Another integral-asdsa.jpg  
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Junior Member
    Joined
    Dec 2006
    Posts
    74
    Quote Originally Posted by totalnewbie View Post
    another problem
    You try to use an incorrect substitution. You should try x=sec u(=1/cos u)
    dx=sec u *tan u* du
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Forum Admin topsquark's Avatar
    Joined
    Jan 2006
    From
    Wellsville, NY
    Posts
    9,937
    Thanks
    338
    Awards
    1
    Quote Originally Posted by totalnewbie View Post
    another problem
    Didn't you post this earlier? Hmmm...Might have been someone else.

    Anyway...

    \int \frac{dx}{x \sqrt{x^2 - 1}}

    Let x = \frac{1}{t}. Then dx = -\frac{dt}{t^2}.

    \int \frac{dx}{x \sqrt{x^2 - 1}} = \int \frac{ -\frac{dt}{t^2}}{ \frac{1}{t} \sqrt{ \frac{1}{t^2} - 1 } }  = - \int \frac{dt}{t \sqrt{\frac{1}{t^2} - 1}} = - \int \frac{dt}{\sqrt{t^2 \left ( \frac{1}{t^2} - 1 \right ) }}

    = \int \frac{dt}{\sqrt{1 - t^2}}

    Do you recognize this integral?

    -Dan
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 2
    Last Post: August 31st 2010, 07:38 AM
  2. Replies: 1
    Last Post: June 2nd 2010, 02:25 AM
  3. Replies: 0
    Last Post: May 9th 2010, 01:52 PM
  4. Replies: 0
    Last Post: September 10th 2008, 07:53 PM
  5. Replies: 6
    Last Post: May 18th 2008, 06:37 AM

Search Tags


/mathhelpforum @mathhelpforum