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Trigonometric Ratio and Identites question

2022 · 27 Jun · Shift 1 · Q34

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JEE Main
Mathematics
Trigonometric Ratio and Identites
2022 · 27 Jun · Shift 1 · Q34

Trigonometric Ratio and Identites question

2022 · 27 Jun · Shift 1 · Q34

JEE MainMathematicsTrigonometric Ratio and IdentitesMCQ+4 / −1

The value of

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

is equal to :

A
$-$ 1
B
$-{1 \over 2}$
C
$-{1 \over 3}$
D
$-{1 \over 4}$

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