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Math Help - Help with trig equations?

  1. #1
    Newbie
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    Feb 2010
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    Help with trig equations?

    I need help with doing these. Please show working out.
    Sorry for the multiple questions. I don't know how to do them

    1) 2cos^2 2x + 3sin2x - 3

    2) 3sec^2 3α - tan2α = 5

    3) 3sin2θ + 2sinθ = 0

    4) sin θ - cos (θ/2) = 0
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  2. #2
    Member Mathelogician's Avatar
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    Hi. i am using my phone to answer you, so i cant write much. to solve the 1st, you should convert cosine into sine. then you have a quadratic equation.when solving that,you earn the four general solutions: x=k.pi-pi/12 , x=k.pi+7pi/12 , x=k.pi-pi/4 , x=k.pi+3pi/4. which just the 1st is true! to solve the others, you can use the linke in my signature... .
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