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Homework Help: Trigonometric equations, help? ^^

  1. Aug 9, 2008 #1
    1. The problem statement, all variables and given/known data

    2 cos^2 x + cos x = 0
    tan x = 3^1/2

    2. Relevant equations
    .. ?? Unit circle.

    3. The attempt at a solution
    for the first, well I tried factoring to isolate x, but it really did not work
    i keep making up my own rules that end up messing with the entire equation,
    i know, its not the best method :rolleyes:
    with the second, i used the unit circle (cos, sin) and the principal
    that tan is = to sin/cos, but none of them are equal to the square root of 3..oy
    any help would be much appreciated ^^
  2. jcsd
  3. Aug 9, 2008 #2


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    Science Advisor
    Homework Helper

    Hi Wholewheat458! :smile:

    (have a square-root: √ :smile:)

    There's lots of ways of doing this.

    Divide the first equation by cosx … that gives you cos x = 0 or -1/2.

    Use sec2x = tan2x + 1 … that gives you cosx = ±1/2.

    And you do know an angle with cosx = 1/2, don't you? :wink:
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