1.

Letalpha , betabe such thatpi lt alpha - beta lt 3 pi. Ifsin alpha + sin beta =-(21)/(65) and cos alpha + cos beta =-(27)/(65) , then the value ofcos""(alpha - beta )/(2)is

Answer»

`-(3)/(sqrt(130))`
`(3)/(sqrt(130))`
`(6)/(65)`
`-(6)/(65)`

Answer :A


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