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

  • Thread starter Thread starter 1940LaSalle
  • Start date Start date
Click For Summary
Euler's identity states that exp(iπ) = -1, leading to exp(2iπ) = 1. The discussion highlights a potential misunderstanding when applying natural logarithms, suggesting that ln(exp(2iπ)) = 0, which implies 2iπ = 0. This confusion arises from the properties of logarithms and exponentials, particularly in the complex plane. The inverse of the exponential function is multi-valued, meaning that if e^x = 1, x can equal n2πi for any integer n. The key takeaway is that the complexities of complex numbers can lead to seemingly paradoxical conclusions if not carefully considered.
1940LaSalle
Messages
7
Reaction score
0
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?
 
Mathematics news on Phys.org
In general, ##f^{-1}(f(z))## is not necessarily equal to ##z##. Can you see why?
 
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##.
 
  • Like
Likes 1940LaSalle
Thanks
 
Thread 'Erroneously  finding discrepancy in transpose rule'
Obviously, there is something elementary I am missing here. To form the transpose of a matrix, one exchanges rows and columns, so the transpose of a scalar, considered as (or isomorphic to) a one-entry matrix, should stay the same, including if the scalar is a complex number. On the other hand, in the isomorphism between the complex plane and the real plane, a complex number a+bi corresponds to a matrix in the real plane; taking the transpose we get which then corresponds to a-bi...

Similar threads

  • · Replies 3 ·
Replies
3
Views
4K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K