Results 1 to 4 of 4

Math Help - Intergration Probs

  1. #1
    Newbie
    Joined
    Nov 2007
    Posts
    8

    Intergration Probs

    Hi,
    Im doing Fourier Series atm for an exam on monday!

    And im stuck on intergration by parts.
    X cos n (pi) = ?
    ...........2

    Im prity sure it its get broken apart into X and cos n (pi)
    .................................................. ....................2

    so basically what im asking is what is the integral of Cos n (pi) is it 2 Sin n (pi)
    .................................................. ............................2 .................n

    Sorry for the .... its the only way i could get it to line up correctly!!

    thanks for your time and help
    Follow Math Help Forum on Facebook and Google+

  2. #2
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by madcal87 View Post
    Hi,
    Im doing Fourier Series atm for an exam on monday!

    And im stuck on intergration by parts.
    X cos n (pi) = ?
    2

    Im prity sure it its get broken apart into X and cos n (pi)
    2

    so basically what im asking is what is the integral of Cos n (pi) is it 2 Sin n (pi)
    2 n

    thanks for your time and help
    you mean \cos \frac {n \pi {\color {red}x}}2, right?

    choose x to be the function to differentiate and the cosine the function to integrate.

    thus, \int x \cos \frac {n \pi x}2~dx = \frac {2x}{n \pi} \sin \frac {n \pi x}2 - \frac 2{n \pi} \int \sin \frac {n \pi x}2 ~dx

    now continue
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Nov 2007
    Posts
    8
    Quote Originally Posted by Jhevon View Post

    thus,  - \frac 2{n \pi} \int \sin \frac {n \pi x}2 ~dx
    is the integral of this 2X -cos n(pi)X
    ............................n(pi).........2

    sorry thanks again!
    Follow Math Help Forum on Facebook and Google+

  4. #4
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by madcal87 View Post
    is the integral of this 2X -cos n(pi)X
    ............................n(pi).........2

    sorry thanks again!
    no

    \int \sin \frac {n \pi x}2~dx = - \frac 2{n \pi} \cos \frac {n \pi x}2

    now multiply that by the - \frac 2{n \pi} and continue. note \frac {n \pi}2 is a constant, use substitution if you can't see the integral right away
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. charge probs...
    Posted in the Math Topics Forum
    Replies: 3
    Last Post: January 10th 2011, 08:30 PM
  2. very easy 3 probs ...
    Posted in the Calculus Forum
    Replies: 9
    Last Post: December 23rd 2010, 04:40 AM
  3. complex no probs
    Posted in the Algebra Forum
    Replies: 1
    Last Post: October 22nd 2010, 08:42 AM
  4. Taylor Probs
    Posted in the Calculus Forum
    Replies: 3
    Last Post: May 6th 2008, 11:15 PM
  5. 4 integration probs
    Posted in the Calculus Forum
    Replies: 2
    Last Post: February 28th 2007, 04:14 PM

Search Tags


/mathhelpforum @mathhelpforum