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

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

A

`6//65 `

B

`3//sqrt(130)`

C

`-3//sqrt(130)`

D

`-6//65`

Text Solution

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The correct Answer is:
c
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