1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: 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


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    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
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook