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NDA 2025 · PYQ · Vectors · easy

Let a, b, (a × b) be unit vectors. What is (a·b) equal to?

  1. A.0✓ Correct
  2. B.1/2
  3. C.1
  4. D.3

Explanation

|a×b| = |a||b|sinθ = sinθ (since |a|=|b|=1). Given |a×b|=1, sinθ = 1, so θ = 90°. Therefore a·b = cosθ = 0.
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