Results 1 to 2 of 2
Like Tree1Thanks
  • 1 Post By SlipEternal

Math Help - Trig Identity

  1. #1
    Member
    Joined
    Jan 2010
    Posts
    88

    Trig Identity

    So Im trying to prove the following inequality 8cos3θ6cosθ=1.
    Ive tried a lot of different things, using substitutions for cos3θ, 2cosθ, pretty much everything and I cant seem to prove it.
    Any help would be appreciated.
    Thanks
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Nov 2010
    Posts
    1,857
    Thanks
    720

    Re: Trig Identity

    That is neither an inequality nor an identity. WolframAlpha

    Now, if you want to know for what values of \theta you have 8\cos(3\theta) - 6\cos \theta = 1, that is solvable, but not easy. You wind up with a cubic polynomial, which is solvable, but extremely difficult. Solution
    Thanks from farmeruser1
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. What Trig Identity are these?
    Posted in the Calculus Forum
    Replies: 2
    Last Post: January 10th 2013, 08:08 AM
  2. Trig Identity
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: May 27th 2011, 01:21 AM
  3. Trig Identity
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: August 8th 2010, 11:04 AM
  4. Trig identity?
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: August 7th 2010, 02:23 PM
  5. trig identity help.
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: November 6th 2007, 03:42 AM

Search Tags


/mathhelpforum @mathhelpforum