JEE Main 2019MathematicsDeterminantsMediumMCQ

JEE Main 2019 — Determinants Question with Solution

JEE Main 2019 (12 Apr Shift 2)

Question

A value of θ∈0,π3, for which 1+cos2θsin2θ4 cos6θcos2θ1+sin2θ4 cos6θcos2θsin2θ1+4 cos6θ=0, is

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Show full solutionCorrect option: A
Correct answer
Aπ9

Step-by-step explanation

R1→R1-R2
1-10cos2θ1+sin2θ4cos6θcos2θsin2θ1+4cos6θ=0
R2→R2-R3
1-1001-1cos2θsin2θ1+4cos6θ=0
⇒1+4cos6θ+sin2θ+1cos2θ=0
1+2cos6θ=0⇒cos6θ=-12
6θ=2π3⇒θ=π9

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About this question

This is a previous-year question from JEE Main 2019, covering the Determinants 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.