Answer: a 1 a 2 + b 1 b 2 + c 1 c 2 = 0.
- A a<sub>1</sub>/a<sub>2</sub> = b<sub>1</sub>/b<sub>2</sub> = c<sub>1</sub>/c<sub>2</sub>
- B a<sub>1</sub>a<sub>2</sub> + b<sub>1</sub>b<sub>2</sub> + c<sub>1</sub>c<sub>2</sub> = 0
- C a<sub>1</sub>a<sub>2</sub> = b<sub>1</sub>b<sub>2</sub>
- D a<sub>1</sub>+a<sub>2</sub> = 0
Correct answer: B. a<sub>1</sub>a<sub>2</sub> + b<sub>1</sub>b<sub>2</sub> + c<sub>1</sub>c<sub>2</sub> = 0
Explanation: Perpendicular lines have zero dot product of direction vectors: a<sub>1</sub>a<sub>2</sub> + b<sub>1</sub>b<sub>2</sub> + c<sub>1</sub>c<sub>2</sub> = 0.
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