Question

how to determine angle of vector in plane​

Answer 1

$\huge\underbrace\mathcal\red{ANSWER}$

Since φ = 90° - ψ, then the sine of the angle between the line and the plane is sin φ = cos ψ. Using the formula of the scalar product of vectors and module of vectors in coordinate form, we obtain the formula for calculating the angle between the line and the plane.