JEE Main 2022 (Online) 27th June Morning Shift | Trigonometric Ratio and Identites Question 17 | Mathematics

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 :

$$-$$1

$$-$$$${1 \over 2}$$

$$-$$$${1 \over 3}$$

$$-$$$${1 \over 4}$$

JEE Main 2022 (Online) 26th June Evening Shift

MCQ (Single Correct Answer)

-1

$$16\sin (20^\circ )\sin (40^\circ )\sin (80^\circ )$$ is equal to :

$$\sqrt 3 $$

2$$\sqrt 3 $$

4$$\sqrt 3 $$

JEE Main 2022 (Online) 25th June Evening Shift

MCQ (Single Correct Answer)

-1

The value of 2sin (12$$^\circ$$) $$-$$ sin (72$$^\circ$$) is :

$${{\sqrt 5 (1 - \sqrt 3 )} \over 4}$$

$${{1 - \sqrt 5 } \over 8}$$

$${{\sqrt 3 (1 - \sqrt 5 )} \over 2}$$

$${{\sqrt 3 (1 - \sqrt 5 )} \over 4}$$

JEE Main 2021 (Online) 26th August Evening Shift

MCQ (Single Correct Answer)

-1

The value of

$$2\sin \left( {{\pi \over 8}} \right)\sin \left( {{{2\pi } \over 8}} \right)\sin \left( {{{3\pi } \over 8}} \right)\sin \left( {{{5\pi } \over 8}} \right)\sin \left( {{{6\pi } \over 8}} \right)\sin \left( {{{7\pi } \over 8}} \right)$$ is :

$${1 \over {4\sqrt 2 }}$$

$${1 \over 4}$$

$${1 \over 8}$$

$${1 \over {8\sqrt 2 }}$$

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