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Math Help - Differential equations

  1. #46
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    Quote Originally Posted by Apprentice123 View Post
    Ok. Please look at this site, the imaginary part is different, you know why?
    What site?
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  2. #47
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    Quote Originally Posted by lvleph View Post
    What site?

    I forgot to put the link, sorry
    http://www.stewartcalculus.com/data/...Orders_Stu.pdf
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  3. #48
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    Someone got the imaginary part in problem of th site?
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  4. #49
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    They probably wrote the imaginary part as
     \frac{\sqrt{-c^2 + 4mk}}{2m}
    This is actually correct since the imaginary pary is not going to have the  i = \sqrt{-1}. Thus we have to factor this out of the determinant.
    Last edited by lvleph; December 3rd 2009 at 12:50 PM. Reason: LaTeX error.
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  5. #50
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    Quote Originally Posted by lvleph View Post
    They probably wrote the imaginary part as
     \frac{\sqrt{-c^2 + 4mk}}{2m}
    This is actually correct since the imaginary pary is not going to have the  i = \sqrt{-1}. Thus we have to factor this out of the determinant.
    If we have c^2 > 4mk we has \sqrt{-1} or am I wrong?
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  6. #51
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    No we have to have 4mk > c^2 If that is the case then
     w_1 = \frac{-c}{2m} + \frac{\sqrt{-c^2 + 4mk}}{2m} i
    and
     w_2 = \frac{-c}{2m} - \frac{\sqrt{-c^2 + 4mk}}{2m} i.
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  7. #52
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    Quote Originally Posted by lvleph View Post
    No we have to have 4mk > c^2 If that is the case then
     w_1 = \frac{-c}{2m} + \frac{\sqrt{-c^2 + 4mk}}{2m} i
    and
     w_2 = \frac{-c}{2m} - \frac{\sqrt{-c^2 + 4mk}}{2m} i.

    Not have c^2 > 4mk ?
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  8. #53
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    If c^2>4mk the solution would not be imaginary. Notice the way I have it written already assumes that we have an imaginary solution, and I have factored out the i. That is why it is -c^2 + 4mk instead of c^2 - 4mk.
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  9. #54
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    Quote Originally Posted by lvleph View Post
    If c^2>4mk the solution would not be imaginary. Notice the way I have it written already assumes that we have an imaginary solution, and I have factored out the i. That is why it is -c^2 + 4mk instead of c^2 - 4mk.
    Sorry my confusion. Thanks
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  10. #55
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    Can you help me or have any stuff about Mechanical Vibrations: Beats and Resonance
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  11. #56
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    Do a google book search. I don't know much about mechanical vibration.
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  12. #57
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    Quote Originally Posted by lvleph View Post
    Do a google book search. I don't know much about mechanical vibration.

    I did not find material to calculate the equations and I still do not understand mechanical vibration
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