Return the positive square-root of an array, element-wise.
x : array_like
out : ndarray, optional
y : ndarray
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.)
>>> 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])