Solve Exponentials Problem: ln((V+v)/(V-v)) = 2ctV

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Discussion Overview

The discussion revolves around solving the equation ln((V+v)/(V-v)) = 2ctV, focusing on the manipulation of logarithmic expressions to isolate the variable v. The scope includes mathematical reasoning and problem-solving techniques related to exponentials and logarithms.

Discussion Character

  • Mathematical reasoning
  • Homework-related
  • Technical explanation

Main Points Raised

  • One participant presents the equation ln((V+v)/(V-v)) = 2ctV and seeks assistance in deriving v = V((e^Vct - e^-Vct)/(e^Vct + e^-Vct).
  • Another participant suggests using the laws of logarithms, specifically the property ln(a/b) = ln(a) - ln(b).
  • A participant attempts to manipulate the equation but incorrectly applies logarithmic properties, leading to confusion about the steps taken.
  • There is a correction regarding the misuse of logarithmic identities, emphasizing the need to use the basic definition of logarithms.
  • Another participant reformulates the original equation to \frac{V+v}{V-v}= e^{2ctV} and suggests solving for v from this expression.

Areas of Agreement / Disagreement

Participants express differing views on the correct application of logarithmic properties, with some corrections and clarifications being made. The discussion remains unresolved regarding the correct steps to isolate v.

Contextual Notes

Some participants' manipulations of logarithmic identities contain errors, and there is uncertainty about the correct approach to isolate v. The discussion reflects various interpretations of logarithmic properties and their application in solving the equation.

Nevermore
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I have ln((V+v)/(V-v)) = 2ctV, and I've checked this is right. But how do I go from here to v = V((e^Vct - e^-Vct)/(e^Vct+e^-Vct))? The solutions just give them as successive lines.

(I appreciate that's not the easiest thing to read, it's taken from the 2004 MEI specimen paper for A-level Mechanics 4, if that helps.)
 
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HINT: Laws of logs;

[tex]\ln\frac{a}{b} = \ln|a| - \ln|b|[/tex]
 
OK, so
ln((V+v)/(V-v)) = 2ctV
=> ln(V+v)-ln(V-v) = 2ctV
ln(V)ln(v) - ln(V)/ln(v)
2ln(v) = 2ctV
v = e^Vct

Is this right? Where can I go from here?
 
Nevermore said:
OK, so
ln((V+v)/(V-v)) = 2ctV
=> ln(V+v)-ln(V-v) = 2ctV
ln(V)ln(v) - ln(V)/ln(v)
2ln(v) = 2ctV
v = e^Vct

Is this right? Where can I go from here?

there is something wrong in what u have written... first of all
log(a*b) = log(a) + log(b)...what u have used is log(a+b) = log(a) * log(b)..even after that u have written something wrong...check it once more...
anyway u don't need to use that...use the basic definition of logs...
if ln(a) = b
=> e^b = a
 
In other words,
[tex]\frac{V+v}{V-v}= e^{2ctV}[/tex]
Solve that for v.
 

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