JEE MATHEMATICS MCQ: TRIGONOMETRY RATIOS

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Application +4 | -1

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:

View answer and explanation

Correct option: B

- \frac{1}{2}

Option B (-1/2) is correct because the sum of cosines can be simplified using trigonometric identities to obtain the result -1/2.

More Questions from TRIGONOMETRY RATIOS

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\tan \alpha=\frac{p}{q}

\alpha=6 \beta

\alpha

\frac{1}{2}[p \operatorname{cosec} 2 \beta-q \sec 2 \beta]

\cos 12^{\circ}+\cos 84^{\circ}+\cos 156^{\circ}+\cos 132^{\circ}

\triangle A B C

C

{\sin ^6}\,\,\theta + {\cos ^6}\,\,\theta + 3{\sin ^2}\,\,\theta \,\,{\cos ^2}\,\,\theta

\sin ^2 \frac{A}{2}+\sin ^2 \frac{B}{2}+\sin ^2 \frac{C}{2}=

\sin ^2(A / 2)+\sin ^2(B / 2)-\sin ^2(C / 2)=