# Don't mess with conditional convergence | Summary and Q&A

23.6K views
December 31, 2017
by
blackpenredpen
Don't mess with conditional convergence

## TL;DR

The video explores different ways of organizing positive integers and rearranging the terms in the alternating harmonic series, revealing surprising patterns and results.

## Install to Summarize YouTube Videos and Get Transcripts

### Q: How is the ratio of even numbers different in the different arrangements of positive integers?

In the standard arrangement of positive integers, the ratio of even numbers to all positive integers is 1/2. However, in an alternate arrangement, the ratio becomes 1/3. This observation highlights the variability and potential for different patterns in organizing mathematical sets.

### Q: What is the significance of the alternating harmonic series?

The alternating harmonic series is known to converge conditionally to the natural logarithm of 2. However, by rearranging the terms in a specific order, the resulting series evaluates to three halves times the natural logarithm of 2. This demonstrates the peculiar behavior of conditionally convergent series.

### Q: How does the rearrangement of terms in a conditionally convergent series impact the outcome?

Rearranging the terms in a conditionally convergent series allows for different sums to be obtained. In the case of the rearranged alternating harmonic series, the sum becomes three halves times the natural logarithm of 2 instead of just the natural logarithm of 2. This showcases the flexibility in manipulating the terms of such series.

### Q: What implications do these findings have in mathematics?

The different arrangements of positive integers and the rearrangement of terms in a conditionally convergent series highlight the intricacies and possibilities within mathematics. It underscores the need for careful consideration and understanding when dealing with mathematical series and sets.

## Summary & Key Takeaways

• The video examines two different ways of organizing the set of positive integers and observes that the ratio of even numbers to all positive integers is different in each arrangement.

• The alternating harmonic series, when rearranged in a specific order, yields a result that is three halves times the natural logarithm of 2.

• The video explains how the rearrangement of terms in a conditionally convergent series allows for different outcomes.