Am I misapplying something here? (Exponentials; Euler's identity)

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Discussion Overview

The discussion revolves around the application of Euler's identity and properties of exponentials, particularly focusing on the implications of taking logarithms of complex exponentials. Participants explore the potential misapplication of mathematical principles leading to seemingly contradictory conclusions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant states that according to Euler's identity, exp(iπ) = -1 and exp(2iπ) = (exp(iπ))² = 1, leading to the conclusion that exp(2iπ) = a⁰ = 1 for any real number a ≠ 0.
  • The same participant questions the validity of taking natural logarithms, suggesting that ln(exp(2iπ)) = 2iπ = 0*ln(a) = 0, which implies 2iπ = 0.
  • Another participant points out that the inverse of a function, such as the exponential function, does not necessarily return the original input, hinting at the complexities involved.
  • A further contribution suggests that without complex numbers, one could arrive at a similar paradox by stating that (1)² = 1 = 1⁰ leads to 2 = 0, emphasizing the multi-valued nature of the logarithm in the complex plane.

Areas of Agreement / Disagreement

Participants express differing views on the implications of logarithmic operations on complex exponentials, with some highlighting the multi-valued nature of logarithms while others question the initial reasoning. The discussion remains unresolved regarding the specific misapplication of concepts.

Contextual Notes

Participants note the dependence on the multi-valued nature of logarithmic functions in the complex plane and the potential pitfalls of applying real-number properties to complex exponentials.

1940LaSalle
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TL;DR
Reconciling an apparent (?) paradox in an exponential
We all know from Euler's identity that exp(iπ)=-1. And from the laws of exponents, exp(2iπ)=(exp(iπ))²=1.

Further, for any real number a≠0, a⁰=1.

Then, since two things equal to the same third thing are necessarily equal, exp(2iπ)=(exp(iπ))²=a⁰=1.

Here's where I'm wondering if I've stripped one or more intellectual gears. If we now take natural logarithms, it would seem we get

ln(exp(2iπ)) = 2iπ = 0*ln (a) = 0

That would suggest at first glance that 2iπ = 0, which made me do a double take, to say the least. I realize this may well be fallacious, and I may be guilty of missing something obvious and fundamental. Help me out here (gently, if you would, please): what did I miss?
 
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In general, ##f^{-1}(f(z))## is not necessarily equal to ##z##. Can you see why?
 
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Without using complex numbers at all, you could have said that ##(1)^2 = 1 = 1^0##, so ##2=0##.
The truth is that the inverse of the exponential function is best understood as a multi-valued function in the complex plane. If ##e^x = f(x) = 1##, then ##x## can equal ## n2\pi i ##, for any integer, ##n##.
 
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Thanks
 

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