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Math Help - Solving Trig Equations

  1. #1
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    Solving Trig Equations

    I have a trig equation that has both sin and cos in it, and I have no clue how to solve it.

    I know how to solve it with one (move the numbers to the right, do the inverse), but not with two.

    2cos(2x)-3sin(x)-1=0

    Can anyone point me in the right direction?
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  2. #2
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    Use the identity \displaystyle \cos{2x} = 1 - 2\sin^2{x}.

    Then rearrange to get a quadratic equation in \displaystyle \sin{x} that you can solve.
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  3. #3
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    Thanks for the speedy reply.

    I'm not quite sure what you mean. Where does the square come from in sin x? By quadratic equation, do you mean b^2-4ac?
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  4. #4
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    That's the discriminant. A quadratic equation is of the form ax^2+bx+c=0
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