# Misc 19 - Chapter 10 Class 12 Vector Algebra

Last updated at May 29, 2018 by Teachoo

Last updated at May 29, 2018 by Teachoo

Transcript

Misc 19 If θ is the angle between any two vectors 𝑎 and 𝑏, then 𝑎 ⋅ 𝑏 = 𝑎 × 𝑏 when θ is equal to (A) 0 (B) 𝜋4 (C) 𝜋2 (D) π Given, 𝑎 ⋅ 𝑏 = 𝑎× 𝑏 So, 𝑎 𝑏 cos θ = 𝑎 𝑏 sin θ cos θ = sin θ We know, that cos 𝜋4 = sin 𝜋4 = 1 2 ∴ θ = 𝝅𝟒 Therefore, the angle between the vectors 𝑎 and 𝑏 is 𝜋4, So, option (B) is correct.

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Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.