Return the positive squareroot of an array, elementwise.
Parameters :  x : array_like
out : ndarray, optional


Returns :  y : ndarray

See also
Notes
sqrt has–consistent with common convention–as its branch cut the real “interval” [inf, 0), and is continuous from above on it. (A branch cut is a curve in the complex plane across which a given complex function fails to be continuous.)
Examples
>>> np.sqrt([1,4,9])
array([ 1., 2., 3.])
>>> np.sqrt([4, 1, 3+4J])
array([ 2.+0.j, 0.+1.j, 1.+2.j])
>>> np.sqrt([4, 1, numpy.inf])
array([ 2., NaN, Inf])