How Can You Explore Solutions for ln() with Negative Values?

  • Thread starter Thread starter Alkatran
  • Start date Start date
Click For Summary
The discussion clarifies that the natural logarithm function, ln(x), is only defined for positive values. It highlights the misconception that ln(x)^-1 equals ln(-x), correcting it to state that ln(-x) actually equals ln(-1) + ln(x). The conversation emphasizes that while complex solutions exist for ln(-x), there are no real solutions. Participants acknowledge the confusion surrounding the relationship between negative values and logarithmic functions. Understanding these properties is crucial for accurately exploring solutions involving ln() with negative inputs.
Alkatran
Science Advisor
Homework Helper
Messages
959
Reaction score
0
1/ln(x) = ln(x)^-1 = ln(-x)
ln(-e) = 1/ln(e) = 1/1 = 1

ln() is only defined over positive values, but you can find solutions like so... where's the error.
 
Mathematics news on Phys.org
ln(x)^-1 = ln(-x) is incorrect. You're probably thinking of ln (1/x) = - ln (x)
 
Your trouble is that

\ln (-x) \ne (\ln(x))^{-1})
This is the correct way to do it.
\ln (-x) = \ln(-1 * x) = \ln(-1) + \ln(x)


There will be complex solutions to this but none on the Real line.
 
Thanks, I knew something wasn't right. I should caught on when -x = 1/x :smile:
 
Good morning I have been refreshing my memory about Leibniz differentiation of integrals and found some useful videos from digital-university.org on YouTube. Although the audio quality is poor and the speaker proceeds a bit slowly, the explanations and processes are clear. However, it seems that one video in the Leibniz rule series is missing. While the videos are still present on YouTube, the referring website no longer exists but is preserved on the internet archive...

Similar threads

  • · Replies 3 ·
Replies
3
Views
1K
Replies
10
Views
2K
  • · Replies 44 ·
2
Replies
44
Views
5K
Replies
8
Views
2K
  • · Replies 6 ·
Replies
6
Views
5K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 12 ·
Replies
12
Views
3K
  • · Replies 4 ·
Replies
4
Views
1K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 5 ·
Replies
5
Views
1K