Finding a3 in the Taylor Series for x^3ln(1+x^2)

Click For Summary

Homework Help Overview

The problem involves finding the coefficient a3 in the Taylor series expansion of the function f(x) = x³ln(1+x²) about x = 0. Participants are exploring the nature of Taylor series and the specific coefficients associated with this function.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Some participants discuss the general approach to finding coefficients in a Taylor series, specifically mentioning the Maclaurin series. Questions arise about the implications of evaluating the function and its derivatives at zero, particularly regarding the values of f(0), f'(0), and the higher-order derivatives.

Discussion Status

The discussion is ongoing, with participants questioning the evaluation of derivatives at zero and clarifying terminology related to derivatives. Some have identified that f(0) = 0 and f'(0) = 0, while others are prompted to consider the second and third derivatives.

Contextual Notes

There is uncertainty regarding the behavior of the function and its derivatives at x = 0, which may affect the determination of the Taylor series coefficients. Participants are navigating the implications of these evaluations in the context of the problem.

lmannoia
Messages
30
Reaction score
0

Homework Statement


Let f(x) = x3ln(1+x2), and let the summation (from n=0 to infinity) anxn be the Taylor series for f about 0. Then what is a3?

Homework Equations





The Attempt at a Solution


What?! I definitely don't expect the answer, but does anyone know how I could go about finding this out from the vague information given about the summation?
 
Physics news on Phys.org
lmannoia said:

Homework Statement


Let f(x) = x3ln(1+x2), and let the summation (from n=0 to infinity) anxn be the Taylor series for f about 0. Then what is a3?

Homework Equations





The Attempt at a Solution


What?! I definitely don't expect the answer, but does anyone know how I could go about finding this out from the vague information given about the summation?
How do you normally go about finding the coefficients of the terms in a Taylor's series? In this case, it's a Maclaurin series.
 
It would be f(0)+f1(0)x+f2(0)x^2/2! +f3(0)x^3/3!.. what I'm not getting is, how can I do this when I'd be plugging in zero? Wouldn't all of the coefficients just be zero? Or am I thinking about this in the wrong way?
 
What do you mean by f1(0)? f2(0)? f3(0)? Do you mean f'(0), f''(0), and f'''(0)?

Clearly f(0) = 0, and it turns out that f'(0) = 0. Have you determined what f''(x) and f'''(x) are?
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 27 ·
Replies
27
Views
4K
Replies
5
Views
2K
  • · Replies 10 ·
Replies
10
Views
2K
Replies
6
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
10
Views
2K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 5 ·
Replies
5
Views
3K
Replies
2
Views
3K