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

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

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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