# Introduction

The number system that we are familiar with, is a gradual development from natural numbers to integers, from integers to rational numbers and then after the introduction of irrational numbers, from rational to real numbers. However this real number system is not sufficient to solve equations of the type
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There is no square root for -4. This is what led to the invention of the symbol 'i' (imaginary unit) which represents can be written as
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A number system called complex numbers denoted by C evolved out of this concept and the nomenclature of a complex number was introduced by C.F. Gauss, a German mathematician. The symbol ' i' was first introduced by the famous Swiss mathematician, Leonhard Euler in 1748. 'i' is the first letter of the Latin word "imaginaries" and it is also referred to as "iota", a Greek alphabet. This subject was later developed by many mathematicians like. A.L. Cauchy, B. Riemann, K. Weierstrass and many others.

C. F. Gauss                              Leonard Euler