JEE Main 2016MathematicsVector AlgebraMediumMCQ

JEE Main 2016 — Vector Algebra Question with Solution

JEE Main 2016 (03 Apr)

Question

Let a→, b→ and c→ be three unit vectors such that a→ ×b→ × c→=32b→ + c→. If b→ is not parallel to c→ , then the angle between a→ and b→ is

Choose an option

Show full solutionCorrect option: B
Correct answer
B5π6

Step-by-step explanation

Given,

a→×(b→×c→ )=32 (b→+c→ ) 

⇒a→·c→b→-a→·b→c→=32 b→+32c→

On comparing, we get

-a→·b→=32

⇒a→·b→=-32

⇒a→b→cosθ=-32

Given a→,b→ are unit vector,

a→=b→=1

From equation  i 

cosθ=-32 

⇒cosθ=cos5π6

⇒θ=5π6

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About this question

This is a previous-year question from JEE Main 2016, covering the Vector Algebra chapter of Mathematics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.