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

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)` , 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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