Look at the answer.
The answer is that the cosine of the vector PA and the normal vector N =√2/4, and the normal vector
Look at the answer.
The answer is that the cosine of the vector PA and the normal vector N =√2/4, and the normal vector N refers to the vector perpendicular to the plane PEH.
Assuming that the angle between the vector PA and the normal vector N is α, the angle between the straight line PA and the plane PEH is 90-α.
So sin (90-α) = cos α = √2/4, so the sine value of the angle formed by the straight line PA and the plane PEH is √2/4.