According to the definition of line-plane included angle, the line-plane included angle is equal to the included angle between the straight line and the projection of the straight line in the plane, and it must be an acute angle, so the line-plane included angle cannot be an obtuse angle.

To find this angle, we usually first find a normal vector of the plane, and then calculate the angle between the straight line and the normal vector, which is complementary to the angle between the straight line and the plane.