Answer: a is perpendicular to (b - c).
- A b = c necessarily, in this particular case
- B a is parallel to vector b specifically
- C b - c = 0, meaning b and c are equal
- D a is perpendicular to (b - c)
Correct answer: D. a is perpendicular to (b - c)
Explanation: a.b = a.c means a.(b-c) = 0. So a is perpendicular to (b-c). This does NOT mean 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