Answer: 3.
- A 3
- B 1
- C sqrt(3)
- D 9
Correct answer: A. 3
Explanation: Expand: |a+b+c|² = |a|²+|b|²+|c|²+2(a·b+b·c+c·a). Unit vectors: |a|²=|b|²=|c|²=1. Mutually perpendicular: all dot products = 0. So |a+b+c|² = 1+1+1+0 = 3. Answer: 3.
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