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Homework Help: Use power-reducing formulas to rewrite

  1. Oct 11, 2012 #1
    1. The problem statement, all variables and given/known data
    Use power-reducing formulas to rewrite 152sin^2 x cos^2 x

    2. Relevant equations
    sin^2θ= 1-cos2θ/ 2 and cos^2θ= 1+cos2θ/2

    3. The attempt at a solution
    152(1-cos2x/2)(1+cos2x/2), 152/4 (1^2 - cos^2 2x), 30(1-(1+cos4x/2), and I got 30-30+30cos4x/2 as the answer but the answer is supposed to be 19-19 cos4x. I have no idea how that can be?
  2. jcsd
  3. Oct 11, 2012 #2


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    Welcome to PF!

    Hi Alison! Welcome to PF! :smile:

    (try using the X2 button just above the Reply box :wink:)
    Nooo :redface:

    (but anyway wouldn't it be simpler to start with sin2xcos2x = (sinxcosx)2 ? :wink:)
  4. Oct 11, 2012 #3


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    ##\frac{152} 4 = 38##.
  5. Oct 11, 2012 #4
    Re: Welcome to PF!

    and then what would I do after that? Because I know we are supposed to use the power reducing formulas to solve it
  6. Oct 11, 2012 #5
    Ooh well I guess doing the right math would help me get that...haha thanks for pointing that out! Now I know my mistake!
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