The principal square root 
of a complex number 
is its principal
root with 
.
If 
,
where 
and 
,
then
 |
The principal square root of 0 is 0. For a nonnegative real number, this is the unique nonnegative square root.
For example, the principal square root of 9 is 3, although both 
and 3 are square roots of
9. For a negative real number 
, the principal square root is 
, where 
is the imaginary unit; the
other square root is 
.
