Three Dimensional Geometry Part 2

Let the foot of perpendicular from a pointP(1,2,−1) to the straight line L:

x

1

=

y

0

=

z

−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 α is the acute angle between the lines PN and PQ, then cos‌α is equal to _________.