# 44 Lecture

## Alternating Series; Conditional Convergence

Alternating Series and Conditional Convergence are important concepts in Calculus and Analytical Geometry. An alternating series is a series where the signs of the terms alternate between positive and negative.

## Important Mcq's Midterm & Finalterm Prepration Past papers included

Which of the following series is an alternating series?

a. ? n=1 to ? 1/n^2

b. ? n=0 to ? (-1)^n/n

c. ? n=1 to ? 1/2^n

d. ? n=1 to ? (n+1)/n^2

What is the alternating series test used for?

a. To determine if an alternating series converges

b. To determine if a geometric series converges

c. To determine if a power series converges

d. To determine if a series is telescoping

Which of the following series converges conditionally?

a. ? n=1 to ? (-1)^n/n

b. ? n=1 to ? 1/n

c. ? n=1 to ? (-1)^n/(2n+1)

d. ? n=1 to ? (-1)^n/(n^2+1)

Which of the following statements about a conditionally convergent series is true?

a. The series diverges.

b. The series converges absolutely.

c. The series converges conditionally.

d. The series converges but is not alternating.

Which of the following series is conditionally convergent?

a. ? n=1 to ? (-1)^n/n^2

b. ? n=1 to ? (-1)^n/(2n+1)

c. ? n=1 to ? 1/2^n

d. ? n=1 to ? n/(n+1)

If a series is conditionally convergent, which of the following must be true?

a. The series is alternating.

b. The series is divergent.

c. The series converges absolutely.

d. The series does not converge.

Which of the following is an example of a conditionally convergent series?

a. ? n=1 to ? 1/n^2

b. ? n=1 to ? (-1)^n/n

c. ? n=1 to ? n!

d. ? n=1 to ? (2n)!

Which of the following tests can be used to test for conditional convergence?

a. Integral test

b. Ratio test

c. Comparison test

d. Alternating series test

Which of the following statements is true about a convergent alternating series?

a. The series converges absolutely.

b. The series converges conditionally.

c. The series is divergent.

d. The series is not alternating.

Which of the following is an example of an alternating series that converges conditionally?

a. ? n=1 to ? 1/n^2

b. ? n=1 to ? (-1)^n/(2n+1)

c. ? n=1 to ? (-1)^n/(n^2+1)

d. ? n=1 to ? n/(n+1)

## Subjective Short Notes Midterm & Finalterm Prepration Past papers included

What is an alternating series in calculus?

Answer: An alternating series in calculus is a series where the terms alternate between positive and negative values.

What is the Alternating Series Test?

Answer: The Alternating Series Test is a test used to determine the convergence or divergence of an alternating series. It states that if the absolute value of the terms in an alternating series decrease and approach zero, then the series converges.

What is conditional convergence?

Answer: Conditional convergence is a property of some series in which the series converges, but if the signs of the terms are changed, the series will diverge.

What is the Ratio Test?

Answer: The Ratio Test is a test used to determine the convergence or divergence of a series. It involves taking the limit of the ratio of consecutive terms and comparing it to a threshold value.

What is the Root Test?

Answer: The Root Test is a test used to determine the convergence or divergence of a series. It involves taking the limit of the nth root of the absolute value of the nth term and comparing it to a threshold value.

What is the difference between absolute convergence and conditional convergence?

Answer: Absolute convergence is a property of a series in which the series converges regardless of the order of the terms, while conditional convergence is a property of a series in which the series converges only when the terms are arranged in a specific order.

What is the alternating harmonic series?

Answer: The alternating harmonic series is an alternating series of the form 1 - 1/2 + 1/3 - 1/4 + 1/5 - 1/6 + ..., which converges to ln(2).

What is the limit comparison test?

Answer: The limit comparison test is a test used to determine the convergence or divergence of a series. It involves taking the limit of the ratio of two series and comparing it to a threshold value.

What is the absolute convergence test?

Answer: The absolute convergence test is a test used to determine the convergence or divergence of a series. It involves taking the absolute value of the terms in the series and determining whether the resulting series converges.

What is the significance of conditional convergence?

Answer: Conditional convergence is significant because it shows that the order in which the terms of a series are arranged can affect whether the series converges or diverges. This is important in certain applications of series, such as in Fourier series.

Alternating Series and Conditional Convergence are important concepts in Calculus and Analytical Geometry. An alternating series is a series where the signs of the terms alternate between positive and negative. A series is said to be conditionally convergent if it converges but not absolutely. In this article, we will discuss alternating series and conditional convergence in detail.

### Alternating Series:

An alternating series is a series in which the signs of the terms alternate between positive and negative. That is, the terms of the series are alternatively added and subtracted. An alternating series can be represented as: a1 - a2 + a3 - a4 + a5 - a6 + ....... = ? (-1)^(n+1) an where an is the nth term of the series. An alternating series can converge or diverge. The Alternating Series Test is used to determine the convergence of alternating series.

### Alternating Series Test:

If an alternating series ? (-1)^(n+1) an satisfies the following conditions, then it converges: The sequence {an} is decreasing. lim n?? an = 0. That is, if the terms of the series decrease in absolute value and the limit of the terms is 0, then the alternating series converges. This test can be used to determine if the series converges absolutely or conditionally.

### Conditional Convergence:

A series is said to be absolutely convergent if the series of absolute values of its terms converges. That is, if ? |an| converges, then the series ? an is said to be absolutely convergent. On the other hand, a series is said to be conditionally convergent if it converges but not absolutely. Conditional convergence occurs when the series converges, but the series of absolute values of its terms diverges. That is, if the series ? |an| diverges and ? an converges, then the series ? an is said to be conditionally convergent. The following theorem gives an example of a conditionally convergent series: The Alternating Harmonic Series: ? (-1)^(n+1) 1/n = 1 - 1/2 + 1/3 - 1/4 + ... The Alternating Harmonic Series is conditionally convergent since the series of absolute values of its terms, ? 1/n, diverges. However, the series itself converges to ln 2.

### Conclusion:

Alternating series and conditional convergence are important concepts in Calculus and Analytical Geometry. An alternating series is a series where the signs of the terms alternate between positive and negative, and the Alternating Series Test is used to determine the convergence of an alternating series. A series is said to be conditionally convergent if it converges but not absolutely, and the Alternating Harmonic Series is an example of a conditionally convergent series. Understanding these concepts is essential in the study of calculus and analysis.