Results 1 to 2 of 2

Math Help - Product Rule finding turning point.

  1. #1
    Newbie
    Joined
    Sep 2010
    Posts
    20

    Product Rule finding turning point.

    Hey, I have a test coming up this week and I not sure how to do these two questions.

    If y=3x.cosx , show that the truning point of curve occurs only when x=cos x/sin x
    I got as far as dy/dx = 3(x-3sin3x+cos3x)=0 but then i dont know what to do after that. I am not sure if thats right


    If y=2x^2.cos3x, show that the turning point of curve occurs at point where x=0 and also whenever x= 2cos3x/3sin3x
    I got as fas as dy/dx= 2x(x-3sin3x+2cos3x)=0 then i am not sure what to do next.
    Thanks.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,695
    Thanks
    450
    Quote Originally Posted by MK47 View Post
    Hey, I have a test coming up this week and I not sure how to do these two questions.

    If y=3x.cosx , show that the truning point of curve occurs only when x=cos x/sin x
    I got as far as dy/dx = 3(x-3sin3x+cos3x)=0 but then i dont know what to do after that. I am not sure if thats right


    If y=2x^2.cos3x, show that the turning point of curve occurs at point where x=0 and also whenever x= 2cos3x/3sin3x
    I got as fas as dy/dx= 2x(x-3sin3x+2cos3x)=0 then i am not sure what to do next.
    Thanks.
    \frac{d}{dx} (3x \cdot \cos{x}) = -3x\sin{x} + 3\cos{x}

    set the derivative = 0
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: March 19th 2011, 03:50 AM
  2. Finding asympotes, turning point and domain!
    Posted in the Calculus Forum
    Replies: 22
    Last Post: January 27th 2011, 09:21 AM
  3. Replies: 9
    Last Post: November 9th 2010, 01:40 AM
  4. Need help with finding the turning point
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: June 7th 2010, 12:32 AM
  5. Finding the turning point
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: December 2nd 2009, 05:29 PM

Search Tags


/mathhelpforum @mathhelpforum