Results 1 to 2 of 2

Math Help - substitution problem

  1. #1
    Member Em Yeu Anh's Avatar
    Joined
    Nov 2009
    Posts
    94

    Angry substitution problem

    If f is continuous on [0, \pi], use the substitution u = \pi - x to prove that:

    \int_0^{\pi}xf(sinx)dx = \frac{\pi}{2}\int_0^{\pi}f(sinx)dx

    Completely lost here. du = -1dx and I don't know how to start from there.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member
    Joined
    Dec 2008
    Posts
    319
    From

    \begin{aligned}<br />
u&=\pi-x\\<br />
du&=-dx<br />
\end{aligned}

    we may derive

    \begin{aligned}<br />
x&=\pi-u\\<br />
dx&=-du.<br />
\end{aligned}

    Hope this helps!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. please help with a substitution problem
    Posted in the Calculus Forum
    Replies: 3
    Last Post: May 2nd 2010, 12:42 PM
  2. U substitution problem
    Posted in the Calculus Forum
    Replies: 1
    Last Post: February 24th 2010, 06:10 PM
  3. Substitution problem
    Posted in the Algebra Forum
    Replies: 2
    Last Post: June 10th 2009, 03:03 PM
  4. u-substitution problem
    Posted in the Calculus Forum
    Replies: 5
    Last Post: November 14th 2008, 05:23 AM
  5. Need help with a u-substitution problem
    Posted in the Calculus Forum
    Replies: 12
    Last Post: September 23rd 2008, 05:09 PM

Search Tags


/mathhelpforum @mathhelpforum