中等MATH-TRIG-009
If a line makes an angle α with the normal to a plane, the angle between the line and the plane is
A. α
B. 2α
C. the angle between the line and any line in the plane
D. 90° − α✓ 答案
解說
The angle between a line and a plane is the complement of the angle between the line and the normal to the plane. It is not α itself, and it is not the angle with an arbitrary line in the plane.