Results 1 to 6 of 6

Math Help - integration

  1. #1
    Newbie
    Joined
    Jun 2011
    Posts
    11

    integration

    integral( e^x*sin x*cos x*cos 2x*cos 4x) dx
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member girdav's Avatar
    Joined
    Jul 2009
    From
    Rouen, France
    Posts
    675
    Thanks
    32
    Use \sin (2a)=2\sin a\cos a to simplify the function, then integrate by parts.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Behold, the power of SARDINES!
    TheEmptySet's Avatar
    Joined
    Feb 2008
    From
    Yuma, AZ, USA
    Posts
    3,764
    Thanks
    78
    Quote Originally Posted by prat View Post
    integral( e^x*sin x*cos x*cos 2x*cos 4x) dx
    Hint:

    \sin(\alpha)\cos(\alpha)=\frac{1}{2}\sin(2\alpha)

    Use this identity 3 times then integrate!
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Jun 2011
    Posts
    11
    what will we do of e^x can yu show me some steps
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Super Member girdav's Avatar
    Joined
    Jul 2009
    From
    Rouen, France
    Posts
    675
    Thanks
    32
    Have you done the simplification? What did you get?
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by prat View Post
    what will we do of e^x can yu show me some steps
    From post #2: "then integrate by parts".

    And I endorse the sentiments expressed in the previous: "Have you done the simplification? What did you get?"
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 3
    Last Post: November 3rd 2010, 12:54 AM
  2. Replies: 2
    Last Post: November 2nd 2010, 04:57 AM
  3. Replies: 8
    Last Post: September 2nd 2010, 12:27 PM
  4. Replies: 2
    Last Post: February 19th 2010, 10:55 AM
  5. Replies: 6
    Last Post: May 25th 2009, 06:58 AM

Search Tags


/mathhelpforum @mathhelpforum