### Imaginary unit

The actual definition of the **imaginary unit** *i* is

It is a square with a negative value. We do not understand what this means, but you can make computations with it.

##### Explanation

Formally you can define *i* as the square root of –1 , so

whatever that may be. This definition is clearly outdated, but is still used in school-books. You never see

as *i* has no real value.

##### Example 1

By coincedence, the result of the calculation

is correct, but is wrong, as you treat *i* like a real value, what it is not. Moreover, parentheses must be solved from inside to outside.

## HistoryThe Swiss mathematician Leonhard Euler (1707 - 1783) used the letter |