CalculusLesson 1 of 2 in the course Sequences and series

Taylor Series: Construction, Convergence, and Applications

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

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Summary

This lesson introduces Taylor series as a way to express a function using its derivatives at one point. It also explains Taylor polynomials and the special case called a Maclaurin series.

A Taylor series for a function ff centered at aa is the power series

f(x)=∑n=0∞f(n)(a)n!(x−a)n,f(x)=\sum_{n=0}^{\infty}\frac{f^{(n)}(a)}{n!}(x-a)^n,

when the series converges. Here, f(n)(a)f^{(n)}(a) is the nnth derivative evaluated at aa, and n!n! is the factorial of nn. The zeroth derivative means the function itself, so f(0)(a)=f(a)f^{(0)}(a)=f(a).

All flashcards

What is a Taylor series centered at aa?
A power series with terms f(n)(a)n!(x−a)n\frac{f^{(n)}(a)}{n!}(x-a)^n, formed from derivatives of ff at aa.
What is a Taylor polynomial of degree nn?
The finite Taylor sum through degree nn, matching the function and its first nn derivatives at the center.
What does the radius of convergence describe?
For a power series, it separates the region of absolute convergence from the region of divergence; boundary behavior is checked separately.
What does it mean for a function to be analytic at a point?
The function equals a convergent power series in some neighborhood of that point.
When is a Puiseux series useful?
It represents certain expansions near algebraic branch points using fractional powers.

Quiz questions

  1. For a power series centered at aa with radius of convergence RR, what is guaranteed when ∣x−a∣<R|x-a|<R?Answer: The series converges absolutely.
  2. Which statement distinguishes analyticity from infinite differentiability for real functions?Answer: An analytic function equals its convergent Taylor series near the point; a smooth function need not.
  3. Within a power series' region of convergence, what happens to its radius after term-by-term differentiation?Answer: The radius of convergence remains unchanged.
  4. In a multivariable second-order Taylor expansion, what does the Hessian matrix organize?Answer: The second partial derivatives and their contributions to the quadratic terms.
  5. Which type of expansion can include negative powers near a singularity?Answer: A Laurent series.

Based on the Wikipedia article Taylor series, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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