JEE Main 2021MathematicsTrigonometric Ratios & IdentitiesEasyMCQ

JEE Main 2021 — Trigonometric Ratios & Identities Question with Solution

JEE Main 2021 (31 Aug Shift 1)

Question

cosec18° is a root of the equation:

Choose an option

Show full solutionCorrect option: A
Correct answer
Ax2-2x-4=0

Step-by-step explanation

We know that 

sin18°=5-14

cosec18°=1sin18° = 45-1

Rationalizing denominator

=45-1×5+15+1

=45+14

=5+1

Hence equation x=5+1

⇒(x-1)2=5

⇒x2-2x+1 = 5
⇒x2-2x-4=0

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About this question

This is a previous-year question from JEE Main 2021, covering the Trigonometric Ratios & Identities 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.