Results 1 to 4 of 4

Thread: Solving an equation in a specified interval

  1. #1
    Newbie
    Joined
    Jun 2008
    Posts
    23

    Solving an equation in a specified interval

    The Question: Solve the equation in the interval 0 < θ < 2 pi.

    cos θ + cos2 θ + sin2 = 0

    Attempted Solution: Well, my hunch was to factor this equation. But, at least to my innumerate eye, it looks as if it cannot be factored. I am a bit confused by the structure of this equation. I'm not use to seeing anything like "sin" without a θ. The answers probably really easy and maybe it's just tiredness preventing me from seeing the solution, but could someone help?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    16,216
    Thanks
    3702
    is the middle term $\displaystyle \cos(2\theta) $ or $\displaystyle \cos^2{\theta}$ ?

    btw, $\displaystyle \sin(2)$ is just a constant.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Jun 2008
    Posts
    23
    Quote Originally Posted by skeeter View Post
    is the middle term $\displaystyle \cos(2\theta) $ or $\displaystyle \cos^2{\theta}$ ?

    btw, $\displaystyle \sin(2)$ is just a constant.
    It's $\displaystyle \cos^2{\theta}$.

    Sorry about the error.

    Equation rewritten:

    $\displaystyle \cos{\theta}$ + $\displaystyle \cos^2{\theta}$ + $\displaystyle \sin^2$.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    16,216
    Thanks
    3702
    $\displaystyle \cos^2{\theta} + \cos{\theta} + \sin(2) = 0$

    looks quadratic to me ...

    only problem is $\displaystyle b^2 - 4ac < 0$

    what's that tell you?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Solving an interval for s^2
    Posted in the Algebra Forum
    Replies: 3
    Last Post: Mar 12th 2011, 01:00 PM
  2. Solving Inequality in Interval Notation
    Posted in the Calculus Forum
    Replies: 1
    Last Post: Aug 24th 2009, 05:29 PM
  3. Replies: 4
    Last Post: Feb 7th 2009, 10:10 AM
  4. Solving for x in the given interval NEED HELP !!!
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: May 13th 2008, 10:34 AM
  5. Solving for Interval [0, 2pi)
    Posted in the Trigonometry Forum
    Replies: 5
    Last Post: May 8th 2006, 02:07 PM

Search Tags


/mathhelpforum @mathhelpforum