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Math Help - Trig Problem

  1. #1
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    Trig Problem

    Hey can you show me how to find the x- Intercepts for cos(y+Pi) = x^2 -x - 7

    I tried a bunch of different things but I can't figure it out: the answer is supposed to be 3 (I like the faces )
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Mudd_101 View Post
    Hey can you show me how to find the x- Intercepts for cos(y+Pi) = x^2 -x - 7

    I tried a bunch of different things but I can't figure it out: the answer is supposed to be 3 (I like the faces )
    as always, x-intercepts occur where y = 0. so plug in y = 0, we have

    \cos \pi = x^2 - x - 7

    \Rightarrow -1 = x^2 - x - 7

    \Rightarrow x^2 - x - 6 = 0

    just solve this quadratic equation for your intercepts (there are 2 answers)
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  3. #3
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    Quote Originally Posted by Mudd_101 View Post
    Hey can you show me how to find the x- Intercepts for cos(y+Pi) = x^2 -x - 7

    I tried a bunch of different things but I can't figure it out: the answer is supposed to be 3 (I like the faces )
    It intercepts the x axis when y is zero!

    \cos(0+\pi) = x^2 -x - 7

    \cos(\pi) = x^2 -x - 7

    -1 = x^2 -x - 7

     x^2 -x - 6 = 0

     (x-3)(x+2) = 0

     x = 3 \text{ or } x = -2
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  4. #4
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    OO thanks (silly me put x as 0)
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