Chapter 9: Problem 1
Suppose you use a second-order Taylor polynomial centered at 0 to approximate a function \(f\). What matching conditions are satisfied by the polynomial?
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Chapter 9: Problem 1
Suppose you use a second-order Taylor polynomial centered at 0 to approximate a function \(f\). What matching conditions are satisfied by the polynomial?
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Let $$f(x)=\sum_{k=0}^{\infty} x^{k}=\frac{1}{1-x} \quad \text { and } \quad S_{n}(x)=\sum_{k=0}^{n-1} x^{k}$$ The remainder in truncating the power series after \(n\) terms is \(R_{n}(x)=f(x)-S_{n}(x),\) which depends on \(x\) a. Show that \(R_{n}(x)=x^{n} /(1-x)\) b. Graph the remainder function on the interval \(|x|<1\) for \(n=1,2,3 .\) Discuss and interpret the graph. Where on the interval is \(\left|R_{n}(x)\right|\) largest? Smallest? c. For fixed \(n,\) minimize \(\left|R_{n}(x)\right|\) with respect to \(x .\) Does the result agree with the observations in part (b)? d. Let \(N(x)\) be the number of terms required to reduce \(\left|R_{n}(x)\right|\) to less than \(10^{-6} .\) Graph the function \(N(x)\) on the interval \(|x|<1 .\) Discuss and interpret the graph.
Given the power series
$$\frac{1}{\sqrt{1-x^{2}}}=1+\frac{1}{2} x^{2}+\frac{1 \cdot 3}{2 \cdot 4}
x^{4}+\frac{1 \cdot 3 \cdot 5}{2 \cdot 4 \cdot 6} x^{6}+\cdots$$
for \(-1
Functions to power series Find power series representations centered at 0 for the following functions using known power series. Give the interval of convergence for the resulting series. $$f(x)=\ln \sqrt{4-x^{2}}$$
a. Use any analytical method to find the first four nonzero terms of the Taylor series centered at 0 for the following functions. You do not need to use the definition of the Taylor series coefficients. b. Determine the radius of convergence of the series. $$f(x)=x^{2} \cos x^{2}$$
Functions to power series Find power series representations centered at 0 for the following functions using known power series. Give the interval of convergence for the resulting series. $$f(x)=\tan ^{-1}\left(4 x^{2}\right)$$
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