8: Sequences and Series
- Page ID
- 175604
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)The topic of infinite series may seem unrelated to differential and integral calculus. In fact, an infinite series whose terms involve powers of a variable is a powerful tool that we can use to express functions as “infinite polynomials.” We can use infinite series to evaluate complicated functions, approximate definite integrals, and create new functions. In addition, infinite series are used to solve differential equations that model physical behavior, from tiny electronic circuits to Earth-orbiting satellites.
- 8.1: Improper Integrals
- This section covers improper integrals, focusing on integrals with infinite limits or integrands with infinite discontinuities. It explains how to evaluate these integrals by taking limits and determining whether they converge or diverge. The section provides examples of both types of improper integrals, illustrating the steps needed to handle these situations effectively in calculus.
- 8.2: Sequences
- This section introduces sequences, defining them as ordered lists of numbers generated by functions with natural numbers as inputs. It covers various types of sequences, including arithmetic and geometric, and explains how to represent sequences explicitly and recursively. The section also discusses limits of sequences and provides examples to illustrate how sequences behave, helping readers understand convergence and divergence.
- 8.3: Infinite Series
- This section introduces infinite series, explaining how to sum an infinite sequence of numbers and when such series converge or diverge. It covers geometric and harmonic series, tests for convergence like the nth-term test and the p-series test, and provides examples of series that converge or diverge. Key concepts include understanding partial sums and using these techniques to analyze infinite series in calculus.
- 8.4: The Divergence and Integral Tests
- This section introduces the Divergence and Integral Tests for determining the convergence or divergence of infinite series. The Divergence Test checks if a series diverges when terms don’t approach zero, while the Integral Test compares a series to an improper integral to assess convergence. Examples illustrate applying these tests effectively to various series.
- 8.5: The Comparison Tests
- This section explains the Direct and Limit Comparison Tests for determining the convergence or divergence of series. The Direct Comparison Test involves comparing terms with a known series, while the Limit Comparison Test uses the limit of the ratio between terms of two series. Examples illustrate how to apply these tests effectively to assess series convergence.
- 8.6: The Alternating Series Test
- This section introduces the Alternating Series Test, which is used to determine the convergence of series with terms that alternate in sign. The test requires that the terms decrease in absolute value and approach zero. It explains how to apply this test to verify the convergence of alternating series and provides examples to illustrate its use in identifying convergent series.
- 8.7: The Ratio and Root Tests
- This section covers the Ratio and Root Tests, both of which are used to determine the convergence or divergence of series. The Ratio Test examines the limit of the ratio between consecutive terms, while the Root Test involves the nth root of terms. These tests are particularly useful for series with factorials or exponential terms. Examples illustrate how to apply each test effectively for assessing series convergence.
Thumbnail: For the alternating harmonic series, the odd terms \(S_{2k+1}\) in the sequence of partial sums are decreasing and bounded below. The even terms \(S_{2k}\) are increasing and bounded above.