Flashcard: Infinite Series and Taylor Methods — 61 carte

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1Domanda

What is an infinite sequence in mathematics?

Risposta

An ordered list of numbers indexed by positive integers or another integer set.

2Domanda

When does a sequence converge to a limit L?

Risposta

When its terms become arbitrarily close to L as n approaches infinity.

3Domanda

What happens if a sequence has no finite limit?

Risposta

The sequence diverges.

4Domanda

For which values of r does the sequence r^n converge?

Risposta

For all r with -1 < r ≤ 1.

5Domanda

What is the limit of the sequence r^n when -1 < r < 1?

Risposta

The limit is 0.

6Domanda

What is the limit of the sequence r^n when r = 1?

Risposta

The limit is 1.

7Domanda

What does the Monotonic Sequence Theorem state?

Risposta

Every bounded monotonic sequence converges.

8Domanda

Which monotonic sequences are guaranteed to converge?

Risposta

Increasing sequences bounded above and decreasing sequences bounded below.

9Domanda

How is an infinite series defined?

Risposta

By its partial sums.

10Domanda

When does an infinite series converge?

Risposta

When its partial sums approach a finite real number.

11Domanda

What is the formula for the nth partial sum?

Risposta

s_n = sum of a_i from i=1 to n.

12Domanda

When does the geometric series sum ar^(n-1) converge?

Risposta

When the absolute value of r is less than 1.

13Domanda

What is the sum of a convergent geometric series?

Risposta

a divided by (1 minus r).

14Domanda

What happens if the limit of a_n is nonzero or does not exist?

Risposta

The series sum a_n diverges.

15Domanda

What if a_n approaches zero in the series sum a_n?

Risposta

The test is inconclusive.

16Domanda

Does the harmonic series sum 1/n converge or diverge?

Risposta

It diverges even though its terms approach zero.

17Domanda

What conditions on f ensure sum a_n and integral of f share convergence?

Risposta

f must be continuous, positive, and decreasing on the relevant tail.

18Domanda

When does the p-series sum 1/n^p converge?

Risposta

It converges when p is greater than 1.

19Domanda

When does the p-series sum 1/n^p diverge?

Risposta

It diverges when p is less than or equal to 1.

20Domanda

What inequality bounds the remainder R_n for a positive decreasing series?

Risposta

The remainder satisfies ∫_{n+1}^∞ f(x) dx ≤ R_n ≤ ∫_n^∞ f(x) dx.

21Domanda

What is the integral remainder bound for the series sum 1/n^3?

Risposta

R_n is at most 1 divided by 2 n squared.

22Domanda

How many terms guarantee error below 0.0005 for sum 1/n^3 using integral remainder?

Risposta

At least 32 terms guarantee the error is below 0.0005.

23Domanda

What happens if 0 ≤ a_n ≤ b_n and sum b_n converges?

Risposta

Sum a_n converges.

24Domanda

What happens if a_n ≥ b_n ≥ 0 and sum b_n diverges?

Risposta

Sum a_n diverges.

25Domanda

What does the limit comparison test say if limit of a_n/b_n is c with 0 < c < ∞?

Risposta

Sum a_n and sum b_n both converge or both diverge.

26Domanda

How do you compare rational or algebraic terms to a p-series?

Risposta

Compare dominant powers of n and choose bounds for convergence or divergence.

27Domanda

What inequality holds if 0 ≤ a_k ≤ b_k for every k > n?

Risposta

Tail remainder R_n of sum a_k is at most tail T_n of sum b_k.

28Domanda

When does the alternating series sum (-1)^n b_n converge?

Risposta

It converges when b_n is decreasing and approaches zero.

29Domanda

What inequality bounds the remainder of an alternating series meeting test conditions?

Risposta

The remainder satisfies |R_n| ≤ b_{n+1}.

30Domanda

What defines absolute convergence of a series?

Risposta

Absolute convergence occurs when the sum of |a_n| converges.

31Domanda

What defines conditional convergence of a series?

Risposta

Conditional convergence occurs when sum a_n converges but sum |a_n| diverges.

32Domanda

What happens to the sum of an absolutely convergent series under rearrangement?

Risposta

Its sum remains the same after any rearrangement.

33Domanda

How does rearranging a conditionally convergent series affect its sum?

Risposta

Rearranging can change the sum of a conditionally convergent series.

34Domanda

What is the first step in classifying a series for convergence?

Risposta

Inspect the term limit.

35Domanda

Which tests are suggested for factorials and constant-to-n terms?

Risposta

The Ratio Test.

36Domanda

For which term form is the Root Test suggested?

Risposta

Terms of the form (b_n)^n.

37Domanda

Why is the Ratio Test not recommended for p-series?

Risposta

Because the ratio a_(n+1)/a_n tends to 1.

38Domanda

What is the geometric series template for |x|<1?

Risposta

1/(1-x) equals the sum from n=0 to infinity of x^n.

39Domanda

How can new power-series representations be obtained?

Risposta

By substituting an expression for x into a known series and adjusting convergence conditions.

40Domanda

How is the derivative of a power series inside its radius of convergence expressed?

Risposta

The derivative equals the sum from n=1 to infinity of n c_n (x-a)^(n-1).

41Domanda

What happens to the radius of convergence after term-by-term differentiation or integration?

Risposta

The radius of convergence remains the same.

42Domanda

What is the coefficient of \((x-a)^n\) in a Taylor series centered at a?

Risposta

It is \(c_n=\frac{f^{(n)}(a)}{n!}\).

43Domanda

What is the formula for the nth Taylor polynomial centered at a?

Risposta

It is \(T_n(x)=\sum_{i=0}^{n}\frac{f^{(i)}(a)}{i!}(x-a)^i\).

44Domanda

When does a formal Taylor series equal the function?

Risposta

Only when the remainder \(R_n(x)\) approaches zero on the interval.

45Domanda

What does Taylor's Inequality state about the remainder \(R_n(x)\)?

Risposta

If \(|f^{(n+1)}(x)| \le M\), then \(|R_n(x)| \le \frac{M|x-a|^{n+1}}{(n+1)!}\).

46Domanda

What is the Maclaurin series formula for e^x?

Risposta

e^x = sum from n=0 to infinity of x^n divided by n!.

47Domanda

What is the radius of convergence for the Maclaurin series of e^x?

Risposta

The radius of convergence is infinite.

48Domanda

What is the Maclaurin series formula for sin x?

Risposta

sin x = sum from n=0 to infinity of (-1)^n x^(2n+1) divided by (2n+1)!.

49Domanda

What is the Maclaurin series formula for cos x?

Risposta

cos x = sum from n=0 to infinity of (-1)^n x^(2n) divided by (2n)!.

50Domanda

What is the radius of convergence for the Maclaurin series of sin x and cos x?

Risposta

Both have infinite radius of convergence.

51Domanda

What is the Maclaurin series formula for arctan x?

Risposta

arctan x = sum from n=0 to infinity of (-1)^n x^(2n+1) divided by (2n+1).

52Domanda

What is the Maclaurin series formula for ln(1+x)?

Risposta

ln(1+x) = sum from n=1 to infinity of (-1)^(n-1) x^n divided by n.

53Domanda

What is the radius of convergence for the Maclaurin series of arctan x and ln(1+x)?

Risposta

Both have radius of convergence equal to 1.

54Domanda

What is the first step to approximate with a Taylor polynomial?

Risposta

Choose a center a.

55Domanda

What is the formula for the linear Taylor approximation T₁(x)?

Risposta

T₁(x) = f(a) + f'(a)(x - a).

56Domanda

How can Taylor approximation error be estimated when a derivative bound is known?

Risposta

By applying Taylor's Inequality.

57Domanda

What is the second-degree Taylor polynomial for f(x) = x^(1/3) centered at 8?

Risposta

T₂(x) = 2 + (1/12)(x - 8) - (1/288)(x - 8)².

58Domanda

What error bound was obtained for the second-degree Taylor polynomial of f(x) = x^(1/3) on [7,9]?

Risposta

|R₂(x)| < 0.0004.

59Domanda

What series is used to approximate (1 + x)^(-1/2) in relativistic kinetic energy?

Risposta

The binomial series.

60Domanda

What substitution is made in the binomial series for relativistic kinetic energy approximation?

Risposta

x = -v²/c².

61Domanda

What does relativistic kinetic energy approximate to when v is much less than c?

Risposta

Approximately (1/2)m₀v².

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