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cos (pi)/(11)+cos (3 pi)/(11)+cos (5 pi)...

`cos (pi)/(11)+cos (3 pi)/(11)+cos (5 pi)/(11)+cos (7 pi)/(11)+cos (9 pi)/(11)=`

A

0

B

`-(1)/(2)`

C

`(1)/(2)`

D

1

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