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The value of cos (2 pi)/(7)+cos (4 pi)/(...

The value of `cos (2 pi)/(7)+cos (4 pi)/(7)+cos (6 pi)/(7)` is

A

1

B

-1

C

`(1)/(2)`

D

`-(1)/(2)`

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HIMALAYA PUBLICATION-MEASUREMENT OF ANGLES, TRIGONOMETRIC RATIOS AND RELATION BETWEEN SIDES AND ANGLES OF A TRIANGLE-QUESTION BANK
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