Math Problem Statement

The Taylor series for f(x) = x^3 at 1 is ∑ c_n (x - 1)^n. Find the first few coefficients.

Solution

The given function is f(x)=x3f(x) = x^3, and we are tasked with finding the Taylor series expansion around x=1x = 1.

Step 1: Taylor Series Definition

The Taylor series of a function f(x)f(x) about x=ax = a is given by: f(x)=n=0cn(xa)nf(x) = \sum_{n=0}^{\infty} c_n (x - a)^n where cnc_n represents the coefficients: cn=f(n)(a)n!c_n = \frac{f^{(n)}(a)}{n!} Here, a=1a = 1 and f(x)=x3f(x) = x^3.

Step 2: Calculate Derivatives

  1. f(x)=x3f(x) = x^3
  2. First derivative: f(x)=3x2f'(x) = 3x^2
  3. Second derivative: f(x)=6xf''(x) = 6x
  4. Third derivative: f(3)(x)=6f^{(3)}(x) = 6
  5. Fourth derivative and higher: f(n)(x)=0f^{(n)}(x) = 0 for n4n \geq 4

Step 3: Evaluate Derivatives at x=1x = 1

We evaluate each derivative at x=1x = 1:

  1. f(1)=13=1f(1) = 1^3 = 1
  2. f(1)=3(1)2=3f'(1) = 3(1)^2 = 3
  3. f(1)=6(1)=6f''(1) = 6(1) = 6
  4. f(3)(1)=6f^{(3)}(1) = 6
  5. f(n)(1)=0f^{(n)}(1) = 0 for n4n \geq 4

Step 4: Find Coefficients

Using the formula cn=f(n)(1)n!c_n = \frac{f^{(n)}(1)}{n!}, we compute the coefficients:

  1. c0=f(1)0!=11=1c_0 = \frac{f(1)}{0!} = \frac{1}{1} = 1
  2. c1=f(1)1!=31=3c_1 = \frac{f'(1)}{1!} = \frac{3}{1} = 3
  3. c2=f(1)2!=62=3c_2 = \frac{f''(1)}{2!} = \frac{6}{2} = 3
  4. c3=f(3)(1)3!=66=1c_3 = \frac{f^{(3)}(1)}{3!} = \frac{6}{6} = 1
  5. c4=f(4)(1)4!=024=0c_4 = \frac{f^{(4)}(1)}{4!} = \frac{0}{24} = 0

Conclusion

The first few coefficients are:

  • c0=1c_0 = 1
  • c1=3c_1 = 3
  • c2=3c_2 = 3
  • c3=1c_3 = 1
  • c4=0c_4 = 0

Would you like more details on how the Taylor series expansion is derived?

Related Questions

  1. How do we compute higher-order coefficients in Taylor series?
  2. Can the Taylor series be used to approximate f(x)=x3f(x) = x^3 near other points besides x=1x = 1?
  3. How does the radius of convergence affect the accuracy of a Taylor series?
  4. What happens if we expand f(x)=x3f(x) = x^3 around a different point, say x=0x = 0?
  5. What is the geometric interpretation of the Taylor series for a cubic function?

Tip:

To approximate functions using Taylor series effectively, focus on finding the terms up to the degree where further terms don't significantly contribute to the result within your desired range of accuracy.

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Math Problem Analysis

Mathematical Concepts

Calculus
Taylor Series
Derivatives

Formulas

f(x) = ∑ c_n (x - a)^n
c_n = f^n(a) / n!

Theorems

Taylor Series Expansion

Suitable Grade Level

Undergraduate Calculus