partial derivative

Discussion in 'Math' started by stupid, Mar 16, 2010.

  1. stupid

    Thread Starter Active Member

    Oct 18, 2009
    81
    0
    hi,
    given f(x,y) = cos(x+y) - sin(x-y),

    find ∂f/∂x.

    is my work right?
    first, convert to
    cos x cos y - sin x sin y -sin x cos y + cos x sin y

    ∂f/∂x= -sin x cos y - cos x sin y - cos x cos y - sin x sin y

    or

    ∂f/∂x = -sin(x+y) - cos(x-y)

    which is right?

    thanks
    stupid
     
  2. steveb

    Senior Member

    Jul 3, 2008
    2,433
    469
    They are both right.
     
  3. stupid

    Thread Starter Active Member

    Oct 18, 2009
    81
    0
    i juz realised my silly question...thanks

    stupid
     
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