JEE Main 2022 · MathsMultiple choiceSingle correctMediumCalculation

JEE Main 27 June 2022, Shift 1, Maths Q18

Question 18 of 90 in this shift, Maths question 18 of 30, Section A.

The value of

\cos\left(\frac{2\pi}{7}\right)+\cos\left(\frac{4\pi}{7}\right)+\cos\left(\frac{6\pi}{7}\right)

is equal to :

(1) $-1$
(2) $-\frac{1}{2}$ Official answer
(3) $-\frac{1}{3}$
(4) $-\frac{1}{4}$

Official answer

Option 2

NTA final key.

Chapter: Trigonometric Functions
Topic: Trigonometric Identities
Idea tested: Trigonometric Sums via Roots of Unity

Same topic in other shifts

All Trigonometric Identities questions

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Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.