Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Satisfying trig equations between (0,2pi)

  1. Oct 19, 2008 #1
    1. The problem statement, all variables and given/known data
    cos^2 x-cos x- 1= 0

    2. Relevant equations
    several trig identities involving cos

    3. The attempt at a solution
    i tried applying identites everywhere, no luck. ive tried using it as a trinomial...no luck....and ive tried adding one to both sides and still no luck....please help lol
  2. jcsd
  3. Oct 19, 2008 #2


    Staff: Mentor

    If you squint your eyes a bit, you might notice that this is a quadratic in cos x. Think about how you would solve x^2 - x - 1 = 0, but keep in mind that you're solving for the cosine of x, not x.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook