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Let alpha, beta be such that it pi < a...

Let `alpha, beta ` be such that it ` pi < alpha - beta <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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A
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