JEE Main 2021MathematicsTrigonometric Ratios & IdentitiesMediumMCQ

JEE Main 2021 — Trigonometric Ratios & Identities Question with Solution

JEE Main 2021 (26 Aug Shift 2)

Question

The value of 2sinπ8sin2π8sin3π8sin5π8sin6π8sin7π8 is :

Choose an option

Show full solutionCorrect option: B
Correct answer
B18

Step-by-step explanation

⇒2sinπ8sin2π8sin3π8sin5π8sin6π8sin7π8

⇒2sinπ8sin2π8sin3π8sinπ-3π8sinπ-2π8sinπ-π8

⇒2sin2π8sin22π8sin23π8

⇒2sin2π8sin22π8sin23π8

⇒2sin2π8sin2π4sin23π8

⇒sin2π8sin23π8

⇒sin2π8sin2π2-π8

⇒sin2π8cos2π8

⇒142sinπ8cosπ82

14sin2π4=18

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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.