## 1.1 Introduction

The theory of sets was developed by German mathematician Georg Cantor (1845-1918). He first encountered sets while working on “problems on trigonometric series”. |

**Examples of sets:- **

**N: **the set of all
natural numbers

**Z: **the set of all
integers

**Q: **the set of all
rational numbers

**R: **the set of real
numbers

**Z ^{+}_{ }: **the set of positive integers

**Q ^{+}: **the set of positive rational numbers, and

**R ^{+}: **the set of positive real numbers.

Last modified: Friday, 24 June 2022, 8:13 PM