return square root of a double-precision value

Contract
Return type	wob
No input parameters.

Water Contract
<method number.double.sqrt/>

See also: sqrt, is_nan

Returns the square root of a _subject of type double as a double .

169.0.<sqrt />

13.0

348.62.<sqrt />

18.671368455472138

If the _subject is negative, sqrt returns a value of NaN (not a number).

-144.842.<sqrt />.<is_nan />

true