# imaginary unit

## Primary tabs

Synonym:
i
Type of Math Object:
Definition
Major Section:
Reference

## Mathematics Subject Classification

### imaginary unit

I would rather say something like:

We define "i" to be a root of f(X)=X^2-1=0. With this choice, the polynomial f has two roots, namely i and -i.

But I guess the entry is fine as it is.

Alvaro

### Re: imaginary unit

sqrt(-1)sqrt(-1)=sqrt((-1)(-1))=sqrt(1)=1
sqrt(-1)sqrt(-1)=i.i=-1
What do you think?

### Re: imaginary unit

Well, sqrt(ab)= sqrt(a)sqrt(b) is only valid for a,b>0?

Of course not.