Results 1 to 2 of 2

Math Help - Solving an Integral of Trig Functions

  1. #1
    Newbie
    Joined
    Sep 2008
    Posts
    3

    Solving an Integral of Trig Functions

    [IMG]file:///C:/Users/Beth/Desktop/integral.jpg[/IMG]


    I have tried to solve this integral using several different trig identities, like the double angle formula, etc. When I use the identities, I am not getting a less complex integral, so I must not be using the right identity. Can someone please suggest a trig identity to use. Thank you.
    Attached Thumbnails Attached Thumbnails Solving an Integral of Trig Functions-integral.jpg  
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member DeMath's Avatar
    Joined
    Nov 2008
    From
    Moscow
    Posts
    473
    Thanks
    5
    Quote Originally Posted by poXGxxi View Post
    I have tried to solve this integral using several different trig identities, like the double angle formula, etc. When I use the identities, I am not getting a less complex integral, so I must not be using the right identity. Can someone please suggest a trig identity to use. Thank you.
    Hint:

    \int {{{\sin }^5}x\,{{\cos }^4}x\,dx}  = \int {\sin x\,{{\sin }^4}x\,{{\cos }^4}x\,dx}  =

    = \int {\sin x{{\left( {1 - {{\cos }^2}x} \right)}^2}{{\cos }^4}x\,dx}  = \left\{ \begin{gathered}<br />
  \cos x = u, \hfill \\<br />
  \sin x\,dx =  - du \hfill \\ <br />
\end{gathered}  \right\} =

    =  - \int {{{\left( {1 - {u^2}} \right)}^2}\,{u^4}\,du}  =  \ldots
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Solving Trig functions?
    Posted in the Trigonometry Forum
    Replies: 8
    Last Post: March 28th 2011, 02:07 PM
  2. Solving trig functions...
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: April 30th 2010, 05:49 AM
  3. Solving x with Trig Functions
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: March 4th 2010, 06:49 AM
  4. solving trig functions sin2x
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: April 22nd 2009, 01:31 AM
  5. Solving Trig Functions?
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: November 9th 2008, 08:16 AM

Search Tags


/mathhelpforum @mathhelpforum