# Very easy question

1. Jul 22, 2011

### footmath

Is it correct ?
$\sqrt{(-1)^2}$ = $\sqrt{(-1)}\sqrt{(-1)}$= $i*i$=$i^2$ =$-1$
or
$\sqrt{(-1)^2}$ = $\sqrt{(1)}$=1

2. Jul 22, 2011

### eumyang

You mean this?
$\text{1) }\sqrt{(-1)^2} = \sqrt{(-1)} \cdot \sqrt{(-1)} = i \cdot i = i^2 = -1$
$\text{2) }\sqrt{(-1)^2} = \sqrt{1} = 1$

Note that the product property of radicals,
$\sqrt{ab} = \sqrt{a} \cdot \sqrt{b}$
holds only if both a and b are non-negative.