Series expansion of logarithmic function

In summary, the conversation discusses finding the first three non-zero terms in the series expansion of ln(5+p) when the argument of the function is small. The suggested method is to write ln(5+p) as ln(1+(4+p)) and expand it, but it may only work if p is approximately -4. The correct approach is to write ln(5+p) as ln(5[1+(p/5)]) and use the properties of logarithms to simplify it into two terms, one of which can be expanded using a series expansion.
  • #1
seboastien
53
0

Homework Statement


Find first three non zero terms in series expansion where the argument of funstion is small

ln(5+p)

Homework Equations





The Attempt at a Solution



The only way I could think how to do this is by saying ln(5+p) = ln(1+(4+p)) and expanding to

(4+p)- 1/2(4+p)^2 + 1/3(4+p)^3 - ... however, I imagine that this would only work if p was approx -4.
 
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  • #2
Come on guys! I really need to know how to do this!
 
  • #3
seboastien said:

Homework Statement


Find first three non zero terms in series expansion where the argument of funstion is small

ln(5+p)

Homework Equations





The Attempt at a Solution



The only way I could think how to do this is by saying ln(5+p) = ln(1+(4+p)) and expanding to

(4+p)- 1/2(4+p)^2 + 1/3(4+p)^3 - ... however, I imagine that this would only work if p was approx -4.
Well, the accuracy, for any finite polynomial expansion, deteriorates as p gets farther from -4 but is the accuracy really relevant? You are only asked to "Find first three non zero terms".
 
  • #4
How do I find the first three non-zero terms of ln(5+p), I'm pretty sure that my answer is wrong.
 
  • #5
You'll want to write this as ln( 5 [ 1+(p/5) ] ) ; then use the properties of logarithms to write it as two terms, one of which is the term you would do the series expansion for.
 
  • #6
Thank you
 

1. What is the series expansion of the logarithmic function?

The series expansion of the logarithmic function is a mathematical representation of the logarithmic function using a sum of terms with increasing powers of the input variable. It is often used to approximate the value of the logarithm for values outside of the range where it can be directly evaluated.

2. How is the series expansion of the logarithmic function derived?

The series expansion of the logarithmic function is derived by using the Taylor series expansion, which is a method of representing a function as an infinite sum of terms. This is done by taking derivatives of the function at a specific point and evaluating them at that point.

3. What is the formula for the series expansion of the logarithmic function?

The formula for the series expansion of the logarithmic function is: ln(x) = (x-1) - (x-1)^2/2 + (x-1)^3/3 - (x-1)^4/4 + ... + (-1)^(n+1)*(x-1)^n/n, where n is the number of terms in the series.

4. How accurate is the series expansion of the logarithmic function?

The accuracy of the series expansion of the logarithmic function depends on the number of terms used in the expansion. The more terms included, the more accurate the approximation will be. However, for values close to the center of expansion, the series will converge faster and be more accurate.

5. What are some applications of the series expansion of the logarithmic function?

The series expansion of the logarithmic function has various applications in mathematics and science, such as in numerical analysis, physics, and engineering. It is also commonly used in computer programs to calculate the logarithm of a number.

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