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(a+ cos ""(pi)/(8)) (1+ cos ""(3pi)/(8))...

`(a+ cos ""(pi)/(8)) (1+ cos ""(3pi)/(8)) (1+ cos "" (5pi)/(8)) (1+ cos ""(7pi)/(8))=`

A

`1/2`

B

`1/4`

C

`1/8`

D

`1/16`

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