**READING: I §2 3**
Back to reading**:**
I §2 2

*begin quote ita***"**

*CHAPTER I* [:]
**
Notions from Set Theory
**

These pages assume that the reader has the book and is reading along. topic index contents

Please read these notes from the beginning to here, and then paragraph 6 of §2.

Please note that, although the exercise has two sub paragraghs, I count the entire exercise as part of the 6th paragraph.

The exercise is to prove that the intersection of complements is equal to the complement of the union. To apply the definition of the equality of sets to the present proof, it is convenient to express it as follows - where the first double arrow has been made vertical for easier reading:

Rosenlicht proves the bottom line, and then the up direction of the vertical double arrow establishes the desired result:

In the first sub paragraph, we suppose that

In the second sub paragraph, we suppose that