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Derivative Method

  1. Jun 3, 2014 #1
    1. The problem statement, all variables and given/known data

    Simplify ##d(log(x^2 + y^2) − z^3)##

    2. Relevant equations

    the derivative?

    3. The attempt at a solution

    The instruction says to simplify. In a similar problem I ended up using the d(a(b-c))= da d(b-c). I am not sure how to deal with the log and only found formulas for ln. Could I just substitute the whole log term with another variable?
  2. jcsd
  3. Jun 3, 2014 #2


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    Gold Member

    d is not the derivative. Its a variable there.
  4. Jun 3, 2014 #3
    The instruction says to simplify the differential. So I assumed it was the derivative?
  5. Jun 3, 2014 #4


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    Homework Helper

    The differential of a function of more variables ##df(x,y,z) =\frac{\partial f}{\partial x}dx+\frac{\partial f}{\partial y}dy+\frac{\partial f}{\partial z}dz.##

    Now ##f(x,y,z) = log(x^2 + y^2) − z^3##. Take the partial derivatives and write up the differential.

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