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    Prove 1+2COS2X +COS4X = 4COS^2COS2X

    Need help
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    asdad
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    (Original post by Mesosleepy)
    Prove 1+2COS2X +COS4X = 4COS^2COS2X

    Need help
    How far did you get? What working do you have so far?
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    (Original post by Mesosleepy)
    Prove 1+2COS2X +COS4X = 4COS^2COS2X

    Need help
    Starting from LHS, try simplifying Cos4x in terms of Cos2x (using the formula for Cos2x, but everything is multiplied by 2 I think).

    The rest is basically further simplifying
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    I don't think its right but

    1+2 [ cos2x +cos 4x ]
    [ 2cos(2x+4x/2)cos(2x-4x/2)] = [2cos(3x)cos(-x)]
    1+2 [2cos(3x)cos(x)] cos(x) because cos(-x) is same as cos(x)
    1+4cos(3x)cos(x)
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    (Original post by kkboyk)
    Starting from LHS, try simplifying Cos4x in terms of Cos2x (using the formula for Cos2x, but everything is multiplied by 2 I think).

    The rest is basically further simplifying
    Wait, so Cos4x becomes 2(Cos2x)
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    Nvm guys I found out how to do it
 
 
 
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