# Arithmetic/Types of Numbers/Imaginary Number

## Imaginary Number

An imaginary number is a number whose square is less than zero.

e.g.

${\displaystyle j={\sqrt {-1}}}$

## Conjugate Number

${\displaystyle -j=-{\sqrt {-1}}}$

## Rules

1) j + j = 2j

2) j - j = 0

3) j x j = -1

4) j / j = 1

5) j + (-j) = 0

6) j - (-j) = 2j

7) j x (-j) = -j2 = 1

8) j / (-j) = -1