We know, the angle between the line and the plane Ax + By + Cz + D=0 is given as,

In this case, l=2, m=1, n= - 2, A=1, B=1, C=0 and D=4.

Putting these values in equation (1) we get,

=45°

Hence, the angle between the line and the plane x + y + 4=0 is 45 ̊