Results 1 to 2 of 2

Math Help - Integrating a trigonometric function!?

  1. #1
    Junior Member
    Joined
    Nov 2009
    Posts
    60

    Integrating a trigonometric function!?

    Trying to integrate fx = (xsin3x) with the limits upper limit=pi/3 and lower limit 0.

    I tried integration by parts but doesnt seem to work out.

    u=x so du= 1
    dv=sin3x so v=-cos3x

    then i tried (uv- /int vdu)

    now im still stuck... answers or help would be much appreciated
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    10,969
    Thanks
    1011
    Quote Originally Posted by Yehia View Post
    Trying to integrate fx = (xsin3x) with the limits upper limit=pi/3 and lower limit 0.

    I tried integration by parts but doesnt seem to work out.

    u=x so du= 1
    dv=sin3x so v=-cos3x

    then i tried (uv- /int vdu)

    now im still stuck... answers or help would be much appreciated
    That's exactly what you do... except if dv = \sin{3x} then v = -\frac{1}{3}\cos{3x}.


    So \int{x\sin{3x}\,dx} = -x\cos{3x} - \int{-\cos{3x}\cdot 1\,dx}

     = -x\cos{3x} + \int{\cos{3x}\,dx}

     = -x\cos{3x} + \frac{1}{3}\sin{3x} + C.


    Now insert your terminals.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Integrating a trigonometric function.
    Posted in the Calculus Forum
    Replies: 2
    Last Post: July 5th 2010, 12:24 AM
  2. Integrating (Inverse Trigonometric Functions)
    Posted in the Calculus Forum
    Replies: 3
    Last Post: June 3rd 2010, 11:27 AM
  3. Integrating this function
    Posted in the Calculus Forum
    Replies: 5
    Last Post: March 11th 2009, 09:08 PM
  4. integrating a function
    Posted in the Calculus Forum
    Replies: 2
    Last Post: February 14th 2009, 07:13 AM
  5. Integrating this function
    Posted in the Calculus Forum
    Replies: 2
    Last Post: March 27th 2008, 11:57 AM

Search Tags


/mathhelpforum @mathhelpforum