Answer: (a.c)b - (a.b)c.
- A (a.c)b - (a.b)c
- B (a.b)c - (a.c)b
- C (b.c)a - (a.b)c
- D (a.c)b + (a.b)c
Correct answer: A. (a.c)b - (a.b)c
Explanation: BAC-CAB rule: a×(b×c) = b(a·c) − c(a·b). Mnemonic: the outer vector a dots with each inner vector. Result lies in the plane of b and c. Answer: (a·c)b − (a·b)c.
Triangle law of vector addition: placing vector b at the head of vector a, the diagonal from the start to the final head gives the resultant a + b.
Concept context
Vectors, dot product, cross product, and geometric applications