Lecture 10: The Completeness of the Real Numbers and Basic Properties of Infinite Series  Summary and Q&A
TL;DR
Convergent and Cauchy sequences are both important in analysis, with convergent sequences having a limit and Cauchy sequences having elements that get close to each other.
Questions & Answers
Q: What is the definition of a Cauchy sequence?
A sequence is Cauchy if for any positive epsilon, there exists a natural number M such that the difference between any two terms with indices n and k greater than or equal to M is less than epsilon.
Q: What is the difference between a convergent and a Cauchy sequence?
A convergent sequence has a limit as n approaches infinity, while a Cauchy sequence has terms that get arbitrarily close to each other.
Q: How do you determine if a series converges?
A series converges if the sequence of partial sums converges, meaning that the sum of the terms in the series approaches a finite number as more terms are added.
Q: What is the relationship between Cauchy sequences and convergent sequences?
A sequence is Cauchy if and only if it is convergent.
Summary & Key Takeaways

A sequence is Cauchy if for any positive epsilon, there exists a natural number M such that the difference between any two terms with indices n and k greater than or equal to M is less than epsilon.

A series is convergent if the sequence of partial sums converges, meaning that the terms of the series add up to a finite number as more terms are added.