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

In summary, the conversation discusses finding the coefficient a3 in the Taylor series for the function f(x) = x3ln(1+x2) about 0. The conversation also touches on the process of finding coefficients in a Taylor series and clarifies the notation used. It is mentioned that f(0) = 0 and f'(0) = 0, and the question is posed whether f''(x) and f'''(x) have been determined.
  • #1
lmannoia
32
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?
 
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  • #2
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.
 
  • #3
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?
 
  • #4
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?
 

1. What is a Taylor series?

A Taylor series is a mathematical representation of a function using an infinite sum of terms. It is used to approximate a function at a specific point by using the values of the function and its derivatives at that point.

2. How is a Taylor series with ln derived?

A Taylor series with ln is derived by taking the natural logarithm of the function and then using the Taylor series formula to expand it into an infinite sum of terms. This series can then be simplified and used to approximate the function.

3. What is the significance of using ln in a Taylor series?

Using ln in a Taylor series allows us to approximate functions that involve logarithmic terms, which are commonly found in mathematical models and scientific calculations. It also allows us to simplify complex functions and make them easier to work with.

4. How accurate is a Taylor series with ln?

The accuracy of a Taylor series with ln depends on the number of terms used in the series. The more terms that are included, the more accurate the approximation will be. However, since it is an infinite series, it can never be 100% accurate.

5. In what fields of science is a Taylor series with ln commonly used?

A Taylor series with ln is commonly used in fields such as physics, chemistry, and engineering to approximate and simplify complex functions. It is also used in statistics and data analysis to model and predict trends in data.

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