Question
Passage: Let a , b , c , a + b , b + c , a + b + c be unit vectors. Question: What is the angle between a and b ?
NDA
Mathematics
Vector Algebra
2026
NDA 2026 (Phase 1)
NDA Mathematics Question (2026) — Solution
Options
- A. 6
- B. 4
- C. 2
- D. 2 3
Answer
D. 2 3
Step-by-step solution
Given | a | = 1, | b | = 1, and | a + b | = 1. Squaring the magnitude of a + b , we get: | a + b |^2 = | a |^2 + | b |^2 + 2| a || b | Substituting the given values: 1^2 = 1^2 + 1^2 + 2(1)(1) 1 = 2 + 2 2 = -1 = - 1 2 = 2 3 Answer: 2 3
Related: Mathematics — Vector Algebra · All PYQ Banks