3d Geometry

Let the foot of perpendicular from a point P(1, 2, \(-\)1) to the straight line \(L:{x \over 1} = {y \over 0} = {z \over { - 1}}\) be N. Let a line be drawn from P parallel to the plane x + y + 2z = 0 which meets L at point Q. If \(\alpha\) is the acute angle between the lines PN and PQ, then cos\(\alpha\) is equal to ________________.