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General Derivative Question

  1. Sep 12, 2011 #1
    Hey guys/ girls and thanks in advance

    Okay this may seem like the dumbest question on the planet. But i figure i better ask before i waste the lecture's time of booking a consult.

    Whats the derivative of

    [itex]y(x) = e^{5ix}[/itex]

    where 5i is a complex number

    both the partial and standard derivative would be

    [itex]\frac{dy}{dx} =\frac{\partial y}{\partial x} = 5i*e^{5ix}[/itex]

    In the notes the 'i' is missed at various stages but he arrives at the correct solution which Ive verified with other sources. Just the derivation i question... since it uses

    [itex]\frac{dy}{dx} =\frac{\partial y}{\partial x} = 5*e^{5ix}[/itex]

    Any particular reason this could even be true.... ??? (Im just thinking a big typo but its over many pages so yea....)

    Cheers Trent
  2. jcsd
  3. Sep 12, 2011 #2


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    Staff Emeritus
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    It is most likely a typo. On the other hand, if he is only looking for the imaginary part of the derivative, then his answer is correct.
    Last edited: Sep 12, 2011
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