Answer: l2 + m2 + n2 = 1.
- A l + m + n = 1
- B lmn = 1
- C l2 + m2 + n2 = 1
- D l2 + m2 + n2 = 0
Correct answer: C. l2 + m2 + n2 = 1
Explanation: The fundamental identity: l2 + m2 + n2 = 1. Direction cosines always satisfy this relation.
Three mutually perpendicular axes x, y, z meeting at the origin O, with a point P located by its (x, y, z) coordinates.
Concept context
Lines and planes in 3D space, direction cosines, distances, and angles