2cos ""(pi)/(13)cos""(9pi)/(13)+cos""(3p...

`2cos ""(pi)/(13)cos""(9pi)/(13)+cos""(3pi)/(13)+cos""(5pi)/(13)=`................ A) `-1` B) `0` C) `1` D) `1/2`

A

`-1`

B

0

C

1

D

`1/2`

Verified by Experts

The correct Answer is:

B

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