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Math Help - Finding the general solution using variation of parameters

  1. #1
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    Finding the general solution using variation of parameters

    The problem:

    y'' + 9y = 9sec^2(3t) 0 < t < pi/6

    So I make it homogenous by setting y''+ 9y = 0

    getting 3i repeating.... y = C1cos(3t)+C2sin(3t)

    From there.. I'm not sure what to do with the 9sec^2(3t). Please help, I have a quiz later today, thanks!
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  2. #2
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    I just realized that I made a mistake.
    I used sin t and cos t and you wanted to use sin (3t) and cos (3t).
    Just assume that was the case and do what I did below.
    Attached Thumbnails Attached Thumbnails Finding the general solution using variation of parameters-picture20.gif  
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