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Homework Help: Strange differentiation

  1. May 6, 2007 #1

    malawi_glenn

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    This is a problem and i show you my work, what i dont understad is how to differentiate things like:

    d(cos(t)) / dp

    attachment.php?attachmentid=9995&stc=1&d=1178475756.jpg

    is all i have done so far madness? or where iam i doing wrong?

    (i did not got the answer myself)
     

    Attached Files:

  2. jcsd
  3. May 6, 2007 #2

    cristo

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    I can't see your attachment (it's not been approved yet) but to perform that derivative, you use the chain rule. So
    [tex]\frac{d}{dp}(\cos t)=-\sin t\frac{dt}{dp}[/tex]
     
  4. May 6, 2007 #3

    HallsofIvy

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    In the attachment, you are also given that p= A/2 sin t so that t= arcsin(2p/A)

    You calculation looks correct except that you have forgotten the "-": d(cos(t))/dt= - sin(t) so -sin(arcsin(2p/A)= -2p/A.
     
  5. May 6, 2007 #4
    HallsofIvy,

    It is a bit frustating that you had the possibility to read the attachement and give a comment on it, while other members have not yet been able to read it because it is "pending".
     
    Last edited: May 7, 2007
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