« Chapter 1: Measure Spaces

Chapter 1: E1.1 Solution

Working problems is a crucial part of learning mathematics. No one can learn topology merely by poring over the definitions, theorems, and examples that are worked out in the text. One must work part of it out for oneself. To provide that opportunity is the purpose of the exercises.
James R. Munkres
’Probability’ for subsets of
Let . Say that has (Cesàro) density and write if exists. Give an example of sets and in for which . Thus, is not an algebra.
If is a subset of such that for every pair of numbers and exactly one number is in , then with . Let be the set of odd numbers. Let be the set that includes , and all even numbers , and all odd numbers . So, Then, the intersection includes and all odd numbers . Let Then, In particular, Therefore, the limit does not exist.