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Partial derivative

  1. Aug 2, 2009 #1
    Given that f(x,y) = x|y|
    I know that fx(x,y) = |y| but what is fy(x,y).
    Thanks heaps.
     
  2. jcsd
  3. Aug 2, 2009 #2

    dx

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    Hint: Break it up into two cases: If y > 0, then f(x,y) = xy. If y < 0, then f(x,y) = -xy.
     
  4. Aug 2, 2009 #3

    HallsofIvy

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    Note that g(y)= |y| is not differentiable at y= 0 so f(x,y)= x|y| has no partial derivative, with respect to y, on the line y= 0.
     
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