Taylor Polynomials: Order 4 for ln(1+x), Derivative Patterns, and Error Analysis

In summary, the conversation involves finding the Taylor polynomial of order 4 for ln(1+x) about 0, writing down Tn(x) of order n by looking at patterns in derivatives, finding the remainder term for Tn(x), and determining the value of n needed to ensure Tn gives a value of ln(1.3) with an error less than 0.0002. The relevant formulas used are Taylor's theorem and the definition of the remainder term. The steps involved include differentiating ln(1+x) to find a pattern, determining the highest term of the Taylor polynomial, and solving for n using the approximation that the absolute value of the remainder term is always less than the absolute value of 1/(n
  • #1
wimma
38
0

Homework Statement


(a) Give Taylor Polynomal of order 4 for ln(1+x) about 0.
(b) Write down Tn(x) of order n by looking at patterns in derivatives in part (a), where n is a positive integer.
(c) Write down the remainder term for the poly. in (b)
(d) How large must n be to ensure Tn gives a value of ln(1.3) which has an error less than 0.0002

Question 2 part d

Homework Equations


The Attempt at a Solution


Okay so we have that the taylor poly is Tn(x) = ∑[f'(a)(x-a)^n]/n! where f' is the nth derivative
And the remainder is Rn(x) = f'(c)(x-a)^(n+1)/(n+1)! where f' is the n+1 th derivative and c lies between x and a
For part a I differentiated ln(1+x) a few times and got a pattern... the values I got at x=0 were 0, 1, -1, 2, -6, 25, -120.
and I got T4 = x - x^2 /2 + x^3 /3 -x^4 /4
b. I got the highest term as (-1)^(n+1) x^n /n
c. I got the remainder term to be (-1)^n (x^(n+1)/(1+c)^(n+1)*(n+1))
d. I got an answer of n=4999 using the approximation that abs(Rn) is always less than abs(1/(n+1))
 
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  • #2
I am afraid I don't have a log in for the university of Sydney.
 
  • #3
Sorry about that
 
  • #4
You want to be taken through the entire exercise, which is fine. However it is not fine to request that without showing your work. So let's start with that, show your work for a b c, write down the formulae you think are relevant. Like Taylor's theorem the definition of the remainder etc.
 
  • #5
Updated
 

Related to Taylor Polynomials: Order 4 for ln(1+x), Derivative Patterns, and Error Analysis

1. What is a Taylor polynomial of order 4?

A Taylor polynomial of order 4 is a mathematical expression that approximates a function using a polynomial of degree 4. It is a way to represent a function as a sum of terms with increasing powers of the input variable. This method is useful for calculating values of a function at a given point, as well as understanding the behavior of the function near that point.

2. What is the Taylor polynomial of ln(1+x) of order 4?

The Taylor polynomial of ln(1+x) of order 4 is given by the formula f(x) = x - x^2/2 + x^3/3 - x^4/4. It is derived by taking the first four terms of the Maclaurin series for ln(1+x) and simplifying them. This polynomial can be used to approximate the value of ln(1+x) for any value of x, as long as x is close to 0.

3. What are the derivative patterns for Taylor polynomials of order 4?

The derivative patterns for Taylor polynomials of order 4 follow a predictable pattern. The nth derivative of a Taylor polynomial of order 4 will be equal to the nth term in the polynomial. For example, the 2nd derivative of f(x) = x - x^2/2 + x^3/3 - x^4/4 is f''(x) = -1 + 2x - x^2. This pattern can be extended to higher order Taylor polynomials as well.

4. How is error analysis used in Taylor polynomials of order 4?

Error analysis is used to determine how accurate the Taylor polynomial of order 4 is in approximating the original function. The error is calculated by finding the difference between the actual value of the function and the value given by the Taylor polynomial. This can help determine how many terms are needed in the polynomial to get a desired level of accuracy.

5. Can Taylor polynomials of order 4 be used for any function?

No, Taylor polynomials of order 4 can only be used for functions that can be represented as a polynomial. Functions that have singularities or do not have a finite number of derivatives cannot be approximated accurately using Taylor polynomials. In these cases, other methods such as power series or numerical methods may be more suitable.

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