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Homework Help: Find the Directional derivative of the function u

  1. Jul 30, 2008 #1
    1. The problem statement, all variables and given/known data

    Hey.
    I need to find the Directional derivative of the function u, in the direction l, in the point m (all in the pic).
    I'm not sure I did it right, can you please give me the ok?


    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     

    Attached Files:

  2. jcsd
  3. Jul 30, 2008 #2

    HallsofIvy

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    Up to DLu= (1/3)(2x- z)+ (2/3)cos y+ (2/3)x, everything looks good. Then you evaluate that at [itex](1,\pi/2, -3)[/itex] and get 7/10? That's not what I get.
     
  4. Jul 30, 2008 #3
    Oops, got 7/3?
     
  5. Jul 30, 2008 #4

    HallsofIvy

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    Science Advisor

    Yes, that is correct. I wondered where that "10" came from!
     
  6. Jul 30, 2008 #5
    Broken calculator...:smile:

    No, just kidding, it was early in the morning.
     
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