JEE Main 2024 Mathematics question
Let a⃗ and b⃗ be two vectors such that |b⃗| = 1 and |b⃗ × a⃗| = 2. Then |(b⃗ × a⃗) − b⃗|² is equal to
Answer: (A)
Solution
b⃗ × a⃗ is perpendicular to b⃗, so |(b⃗ × a⃗) − b⃗|² = |b⃗ × a⃗|² + |b⃗|² − 2 b⃗·(b⃗ × a⃗) = 4 + 1 − 0 = 5.