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Let alpha, beta be such that pi lt alpha...

Let `alpha, beta` be such that `pi lt alpha -beta lt 3 pi.`
If `sin alpha + sin beta =- (21)/(65) and cos alpha + cos beta =- (27)/(65) and ` if the value of `cos "" (alpha - beta)/(2) =(-a)/(sqrtb),` then `a xx b=`

A

`-(3)/(sqrt(130))`

B

`(3)/(sqrt(130))`

C

`(6)/(65)`

D

`-(6)/(65)`

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The correct Answer is:
A
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