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A vector calculus proof question

  1. Jan 8, 2013 #1
    1. The problem statement, all variables and given/known data

    The image contains the problem statement and all relevant equations. I have no idea what to do, this is all very new to me...plus the hint doesnt make sense to me.

    [url=http://postimage.org/][PLAIN]http://s13.postimage.org/b0kq27bkn/photo_6.jpg[/url] photo uploader[/PLAIN]
     
  2. jcsd
  3. Jan 8, 2013 #2

    Dick

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    I think they just want you to show that the dot product of grad(∅) with dr gives you the expression for d(∅) in the expression for the total derivative in the hint.
     
  4. Jan 8, 2013 #3
    I kind of understand what you mean, but not sure what the first step is:confused:
     
  5. Jan 8, 2013 #4

    Dick

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    You've got dr in terms of the unit vectors with the hats on them. Write out grad(phi) in terms of the unit vectors and take the dot product.
     
  6. Jan 9, 2013 #5
    is this what you mean?... i think I was overthinking it , thanks for your help!

    [url=http://postimage.org/][PLAIN]http://s2.postimage.org/rgazdfeih/photo_7.jpg[/url] online photo storage[/PLAIN]
     
  7. Jan 9, 2013 #6

    Dick

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    Yes, I think that's what they want.
     
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