1.

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 value of "cos" (alpha- beta)/(2) is

Answer»

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

Answer :A


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