Results 1 to 3 of 3

Math Help - possible to factor??

  1. #1
    Newbie
    Joined
    Dec 2007
    Posts
    22

    possible to factor??

    I used half angle formula to get from sin (x/2) + cos x = 0 -->
    2cos^2 x - cos x + 1 = 0, but is it possible to factor?

    I graphed the original on my calculator and the answer appears to be x=pi, but I want to understand how to arrive at that answer. I also want to arrive at that answer using the tools I have covered in the class, which at this point means using the half angle formula and trig id's. I have worked out cos (x/2) - sin x = 0 with no problem as I can factor it after using 1/2 angle formula.
    Last edited by dashreeve; July 21st 2008 at 07:34 AM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Aug 2007
    From
    USA
    Posts
    3,110
    Thanks
    2
    Have you NEVER heard of the Quadratic Formula?

    \sqrt{(-1)^{2}-4(2)(1)} = \sqrt{1 - 8} = \sqrt{-7}

    Now what do you think about factoring?

    You studied algebra BEFORE trigonometry for a reason. Do not forget your algebra. You will need it.

    How sure are you that you used the half-ange identity correctly? With that square root in there, are you certain something didn't go wrong?

    You may wish to check out -\frac{\pi}{3} as well.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Super Member

    Joined
    May 2006
    From
    Lexington, MA (USA)
    Posts
    11,659
    Thanks
    599
    Hello, dashreeve!

    I used half-angle formula to get from:

    . . sin(x) + cos(x) .= .0 . . 2cos(x) - cos(x) + 1 .= .0 . . . . Wrong!

    Use the identity: . cosθ .= .1 - 2sin(θ)


    We have: .sin(x) + 1 - 2sin(x) .= .0 . . 2sin(x) - sin(x) - 1 .= .0

    . . which factors: .[sin(x) - 1] [2sin(x) + 1] .= .0


    Got it?

    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 0
    Last Post: July 19th 2011, 11:45 AM
  2. factor analysis , extract second factor loading
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: June 1st 2011, 05:17 AM
  3. factor analysis , extract second factor loading
    Posted in the Differential Geometry Forum
    Replies: 0
    Last Post: May 30th 2011, 05:29 AM
  4. Factor 3x^2 +2x -6
    Posted in the Algebra Forum
    Replies: 8
    Last Post: October 11th 2009, 10:12 AM
  5. How do i factor this?
    Posted in the Algebra Forum
    Replies: 4
    Last Post: September 18th 2008, 02:45 PM

Search Tags


/mathhelpforum @mathhelpforum