Solve ln(a/b+1) Using Identity ln(a+b)=ln b + ln(a/b+1)

  • Context: Undergrad 
  • Thread starter Thread starter Gurasees
  • Start date Start date
  • Tags Tags
    Logarithm
Click For Summary

Discussion Overview

The discussion revolves around the expression "ln(a/b+1)" and its manipulation using the identity "ln(a+b)=ln b + ln(a/b+1)". Participants explore the implications of this identity, particularly in the context of a specific expression involving temperature (T) and logarithmic functions. The scope includes mathematical reasoning and potential numerical solutions.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant questions the meaning of "solve" in relation to the expression, suggesting that the identity leads to repetitive forms.
  • Another participant presents a specific logarithmic expression involving temperature and suggests numerical methods or power series expansion as potential approaches.
  • Several participants express uncertainty about how to simplify or solve the expression further without a specific equation.
  • There are repeated requests for resources or links to help with understanding power series related to logarithmic and exponential functions.
  • One participant emphasizes the importance of considering the interval of convergence when expanding functions into series.
  • Another participant asks about the expansion of ln(x-a) and requests assistance in finding it.

Areas of Agreement / Disagreement

Participants generally agree that the expression cannot be simplified further without an equation. However, there is no consensus on how to approach the problem or what constitutes a solution, leading to multiple competing views on the methods to be used.

Contextual Notes

Participants note the dependence on the variable T and the importance of understanding the range of T-292 for the power series to be applicable. There is also mention of the need for an actual equation to facilitate solving the problem.

Gurasees
Messages
50
Reaction score
1
How to solve "ln(a/b+1)" after applying the identity "ln(a+b)=ln b + ln(a/b+1)" ?
where "ln" is natural log, a and b have variable values in them.
upload_2019-2-23_18-5-12.png
upload_2019-2-23_18-5-12.png
upload_2019-2-23_18-5-12.png
 

Attachments

  • upload_2019-2-23_18-5-12.png
    upload_2019-2-23_18-5-12.png
    63.7 KB · Views: 715
Last edited:
Mathematics news on Phys.org
What do you mean by "solve"?
 
fresh_42 said:
What do you mean by "solve"?
The identity keeps repeating itself in the solution,
I want to take ln of

  • {e^(-6.7/(T-292)) + 0.56/(T-292)} / {3/(T-292)}
 
upload_2019-2-23_18-4-19.png
 

Attachments

  • upload_2019-2-23_18-4-19.png
    upload_2019-2-23_18-4-19.png
    63.7 KB · Views: 446
So you have ##\log \left( (T-292)\exp\left( \dfrac{-6.7}{T-292} \right) + 0.56 \right) - \log(3)\,.##
I think you can only solve this numerically, resp. expand the exponential function and the logarithm into power series, in which case you must consider the interval of convergence.
 
fresh_42 said:
So you have ##\log \left( (T-292)\exp\left( \dfrac{-6.7}{T-292} \right) + 0.56 \right) - \log(3)\,.##
I think you can only solve this numerically, resp. expand the exponential function and the logarithm into power series, in which case you must consider the interval of convergence.
I don't know how to do that. Can you send me some links which might be helpful for the solution?
 
Gurasees said:
I don't know how to do that. Can you send me some links which might be helpful for the solution?
Solution of what? You cannot simplify this expression further. To solve something, an equation would be helpful. You can find the power series on Wikipedia if you look for the exponential, resp. logarithmic function. But look out for the range of ##T-292\,.##
 
I still don't see an equation you could solve. Can you "solve a+b"?
We have an expression that depends on T. Should that be equal to something specific? Do you want to find a T such that the expression will obtain a given value? That will need numerical approximations.
 
  • Like
Likes   Reactions: Gurasees
fresh_42 said:
Solution of what? You cannot simplify this expression further. To solve something, an equation would be helpful. You can find the power series on Wikipedia if you look for the exponential, resp. logarithmic function. But look out for the range of ##T-292\,.##
fresh_42 said:
Solution of what? You cannot simplify this expression further. To solve something, an equation would be helpful. You can find the power series on Wikipedia if you look for the exponential, resp. logarithmic function. But look out for the range of ##T-292\,.##
Thanks for your help.
 
  • #10
fresh_42 said:
Solution of what? You cannot simplify this expression further. To solve something, an equation would be helpful. You can find the power series on Wikipedia if you look for the exponential, resp. logarithmic function. But look out for the range of ##T-292\,.##
I can't find the expansion of ln(x-a). Can you help?
 
  • #11
  • Like
Likes   Reactions: Gurasees

Similar threads

  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 15 ·
Replies
15
Views
4K
  • · Replies 8 ·
Replies
8
Views
2K
Replies
1
Views
2K
  • · Replies 13 ·
Replies
13
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 3 ·
Replies
3
Views
826
  • · Replies 5 ·
Replies
5
Views
4K