Results 1 to 2 of 2

Math Help - critical points

  1. #1
    Member
    Joined
    Oct 2007
    Posts
    178

    critical points

    I apologize. I put this up and then realized the solution. Please delete this.


    Find the critical points.
    f(x)=x^3 - 2x - 2 \cos x
    f'(x)= 3x^2 -2 + 2 \sin x

    So I set the derivatie to 0, to find the critical points, and got:
    3x^2 + 2 sin x - 2 = 0 ... looks like some kind of spooky quadratic equation.
    I know I need to find how those 2 equal 0.
    I don't know how, aside from lots of trial and error.

    Thank yoU!


    edit: solution [SIZE="7"]GRAPH!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by Truthbetold View Post
    Find the critical points.
    f(x)=x^3 - 2x - 2 \cos x
    f'(x)= 3x^2 -2 + 2 \sin x

    So I set the derivatie to 0, to find the critical points, and got:
    3x^2 + 2 sin x - 2 = 0 ... looks like some kind of spooky quadratic equation.
    I know I need to find how those 2 equal 0.
    I don't know how, aside from lots of trial and error.

    Thank yoU!
    There's no exact solution that I can see (it's worth testing x = 0, but no it doesn't work). And life's too short for trial and error (besides, there's no exact solution). Any reason why you can't use technology to get a numerical solution to a required level of accuracy ...... Then it's a cinch.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 16
    Last Post: June 10th 2011, 06:49 AM
  2. Replies: 1
    Last Post: April 20th 2010, 07:36 PM
  3. Replies: 2
    Last Post: October 29th 2009, 08:02 PM
  4. critical points
    Posted in the Calculus Forum
    Replies: 5
    Last Post: October 26th 2009, 08:41 PM
  5. Critical Points
    Posted in the Calculus Forum
    Replies: 7
    Last Post: November 1st 2008, 02:14 PM

Search Tags


/mathhelpforum @mathhelpforum