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Math Help - trig equa solve for x

  1. #1
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    trig equa solve for x

    trig equa solve for x:

    2(sinx)^2 + 7sinx-4=0

    between 0 and 2pi.

    How would yo go about doing this one>?
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  2. #2
    Super Member bigwave's Avatar
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    Cool un FOIL

    Quote Originally Posted by heatly View Post
    trig equa solve for x:

    2(sinx)^2 + 7sinx-4=0

    between 0 and 2pi.

    How would yo go about doing this one>?
    try to un FOIL it

    (2sinx - 1)(sinx + 4) = 0

    the rest is easy...

    2sinx = 1 \rightarrow  sinx = \frac{1}{2} \rightarrow sin^{-1}\left(\frac{1}{2}\right) = \frac{\pi}{6}\ ,\frac{5\pi}{6}

    sinx = -4 is undefined.
    Last edited by bigwave; May 19th 2010 at 10:41 PM. Reason: more steps
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  3. #3
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    Thank you very much,very good.
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  4. #4
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    Thank you very much,very good.
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