### Complex Numbers

**Chapter 1 Introduction
**The

**Complex Numbers**idea is known in antiquity. Heron surface triangle considerations for example. The mathematicians imagined about stranged numbers

**i**in

**XVI..XVII**centuries then. Why strange numbers? Because

**i*i=-1**! This is heresy after all!

The

**complex numbers**was a heresy originally. But it helped to solve many real problems. The alternating currents emerged in

**X**

**IX century**for example. These currents are

**sinusoids**. The complex numbers are very useful to calculate sinusoids–>addition, mutiplying etc. More easier than than simple trigonometry operations.

**Note**

**i**number is known as an

**imaginary**number as a part of the

**complex**number. It’s used by mathematicians. But electricians use

**j**symbol instead. Why? Because

**i**is a current symbol for electricians.

The

**j**as an imaginary number will be used in this article.