Misc 16 - If θ is angle between two vectors a and b, then a.b >= 0

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Misc 16 If θ is the angle between two vectors 𝑎 ⃗ and 𝑏 ⃗ , then 𝑎 ⃗ ⋅𝑏 ⃗ ≥ 0 only when (A) 0 < 𝜃< 𝜋/2 (B) 0 ≤ 𝜃 ≤𝜋/2 (C) 0 < 𝜃 < π (D) 0 ≤𝜃 ≤ 𝜋 Given, 𝑎 ⃗. 𝑏 ⃗ ≥ 0 |𝑎 ⃗ | |𝑏 ⃗ | cos θ ≥ 0 Assuming |𝑎 ⃗ | ≠ 0 and |𝑏 ⃗ | ≠ 0 cos θ ≥ 0/|𝑎 ⃗ ||𝑏 ⃗ | cos θ ≥ 0 ∴ 0 ≤ θ ≤ 𝜋/2 So, (B) is the correct answer

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo