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Area under a curve / Trig Identity Watch

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    http://qualifications.pearson.com/co...e_20130122.pdf

    Question 5 C

    I don't know how to square 3sin2x
    The mark scheme says the answer to it is 9/2(1-cos4x)
    I have no idea how it went to that.
    Urgent help needed, exam tomorrow
    Please explain all your steps so I can understand
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    (Original post by Regret786)
    http://qualifications.pearson.com/co...e_20130122.pdf

    Question 5 C

    I don't know how to square 3sin2x
    The mark scheme says the answer to it is 9/2(1-cos4x)
    I have no idea how it went to that.
    Urgent help needed, exam tomorrow
    Please explain all your steps so I can understand
    (3sin2x)2 = 9sin2(2x)

    Now
    cos 2A = 1 - 2sin2A
    cos 4A = 1 - 2sin22A
    2sin22A = 1 - cos4A

    and hopefully you can finish it
 
 
 
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