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Homework Help: Finding the curl of F

  1. Nov 21, 2011 #1
    1. The problem statement, all variables and given/known data
    1.F=(x-8z)i+(x+9y+z)j+(x-8y)k find the curl of F



    2. Relevant equations
    curl of F= del X F


    3. The attempt at a solution
    1. First I took the partial with respect to y of (x-8y) and subtracted the partial with respect to z of (x+9y+z). From this I got (-8-1) Then I took the partial with respect to x of (x-8y) and subtracted the partial with respect to z of (x-8z), getting (1+8). I then took the partial with respect to x of (x+9y+z) and subtracted the partial with respect to y of (x-8z), getting (1-0). So I took (-8-1)-(1+8)+(1-0) and got an answer of 1, but this was wrong.


    1. The problem statement, all variables and given/known data
    2.F=(7e^x)i-(14e^y)j+(7e^z)k find the curl of F


    2. Relevant equations
    curl of F= del X F


    3. The attempt at a solution
    2. For this, since I was always gonna be taking the partial with respect to a variable that was not in that part of the function, everything would be zero. Ex: partial with respect to x of -14e^y should be zero I believe
     
  2. jcsd
  3. Nov 21, 2011 #2
    For the curl of the first function I think that in finding the jth component of curlF you have to take the partial wrt z of (x-8z) and subtract from this the partial wrt x of (x-8y) but you did the reverse.

    Note also that curl F is a vector and so it must remain as i(...) +j(...) +k(....).
     
    Last edited: Nov 21, 2011
  4. Nov 21, 2011 #3
    Yes the curl of the second function F gives the zero vector.
     
  5. Nov 21, 2011 #4
    I thought so. I entered this in and it was wrong. I'll just try emailing my professor.
     
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