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Ch. 11 - Power Series
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243당신이 사용하는 게 아니라요?교과서 변경
11장, 문제 11.4.38

{Use of Tech} Approximating definite integrals Use a Taylor series to approximate the following definite integrals. Retain as many terms as needed to ensure the error is less than 10⁻⁴.
∫₀⁰ᐧ² sin x² dx

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Recognize that the integral involves the function \( \sin(x^2) \), which does not have an elementary antiderivative, making a Taylor series approximation a suitable approach.
Write the Taylor series expansion of \( \sin z \) around \( z=0 \): \[ \sin z = \sum_{n=0}^{\infty} (-1)^n \frac{z^{2n+1}}{(2n+1)!} = z - \frac{z^3}{3!} + \frac{z^5}{5!} - \cdots \] Substitute \( z = x^2 \) to get the series for \( \sin(x^2) \): \[ \sin(x^2) = x^2 - \frac{x^6}{3!} + \frac{x^{10}}{5!} - \cdots \]
Set up the integral of the series term-by-term from 0 to 0.2: \[ \int_0^{0.2} \sin(x^2) \, dx = \int_0^{0.2} \left( x^2 - \frac{x^6}{3!} + \frac{x^{10}}{5!} - \cdots \right) dx = \sum_{n=0}^{\infty} (-1)^n \frac{1}{(2n+1)!} \int_0^{0.2} x^{4n+2} \, dx \]
Integrate each term using the power rule: \[ \int_0^{0.2} x^{m} \, dx = \frac{(0.2)^{m+1}}{m+1} \] where \( m = 4n + 2 \). So each term becomes: \[ (-1)^n \frac{(0.2)^{4n+3}}{(2n+1)! (4n+3)} \]
Add terms of the series until the absolute value of the next term is less than \( 10^{-4} \) to ensure the error is within the required tolerance. Sum all included terms to approximate the value of the integral.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Taylor Series Expansion

A Taylor series represents a function as an infinite sum of terms calculated from the function's derivatives at a single point. For sin(x²), expanding around x=0 allows approximation by polynomials, making integration manageable. Truncating the series after enough terms controls the approximation error.
추천 영상:
08:42
Taylor Series

Definite Integral Approximation Using Series

Integrating a function approximated by a Taylor series involves integrating each polynomial term individually over the given interval. This method simplifies complex integrals into sums of integrals of powers of x, which are straightforward to compute, enabling approximate evaluation of the definite integral.
추천 영상:
05:43
Definition of the Definite Integral

Error Estimation and Control

When truncating a Taylor series, the remainder term estimates the error between the true function and its polynomial approximation. Ensuring the error is less than 10⁻⁴ requires calculating or bounding this remainder, guiding how many terms to retain for a sufficiently accurate integral approximation.
추천 영상:
04:57
Determining Error and Relative Error
관련 실천
교과서 질문

Find a Taylor series for f centered at 2 given that f⁽ᵏ⁾(2)=1, for all nonnegative integers k.

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교과서 질문

Use of Tech Linear and quadratic approximation


a. Find the linear approximating polynomial for the following functions centered at the given point a.


b. Find the quadratic approximating polynomial for the following functions centered at a.


c Use the polynomials obtained in parts (a) and (b) to approximate the given quantity.


f(x) = 8x^(3/2), a=1; approximate 8 ⋅ 1.1^(3/2)

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교과서 질문

Taylor series Write out the first three nonzero terms of the Taylor series for the following functions centered at the given point a. Then write the series using summation notation.

ƒ(x) = tan⁻¹(4x), a = 0

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교과서 질문

Use of Tech Linear and quadratic approximation


a. Find the linear approximating polynomial for the following functions centered at the given point a.


b. Find the quadratic approximating polynomial for the following functions centered at a.


c Use the polynomials obtained in parts (a) and (b) to approximate the given quantity.


Find the Taylor polynomials p₁, …, p₅ centered at a=0 for f(x)=e⁻ˣ

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교과서 질문

Derivative trick Here is an alternative way to evaluate higher derivatives of a function f that may save time. Suppose you can find the Taylor series for f centered at the point a without evaluating derivatives (for example, from a known series). Then f⁽ᵏ⁾(a)=k! multiplied by the coefficient of (x−a)ᵏ. Use this idea to evaluate f⁽³⁾(0) and f⁽⁴⁾(0) for the following functions. Use known series and do not evaluate derivatives.


f(x) = eᶜᵒˢ ˣ

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교과서 질문

{Use of Tech} Approximating sin x Let f(x)=sin x, and let pₙ and qₙ be nth−order Taylor polynomials for f centered at 0 and π, respectively.

a. Find p₅ and q₅

b. Graph f, p₅, and q₅ on the interval [−π, 2π]. On what interval is p₅ a better approximation to f than q₅? On what interval is q₅ a better approximation to f than p₅?

c. Complete the following table showing the errors in the approximations given by p₅ and q₅ at selected points.

d. At which points in the table is p₅ a better approximation to f than q₅? At which points do p₅ and q₅ give equal approximations to f? Explain your observations.

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