Answer: 2.
- A 1
- B 3
- C 0
- D 2
Correct answer: D. 2
Explanation: l<sup>2</sup>+m<sup>2</sup>+n<sup>2</sup> = 1, where l=cos(alpha) etc. sin<sup>2</sup>(alpha)+sin<sup>2</sup>(beta)+sin<sup>2</sup>(gamma) = (1-cos<sup>2</sup>(alpha))+(1-cos<sup>2</sup>(beta))+(1-cos<sup>2</sup>(gamma)) = 3 - (l<sup>2</sup>+m<sup>2</sup>+n<sup>2</sup>) = 3 - 1 = 2.
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