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

Let ` alpha , beta ` be such ` 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

`(6)/( 65)`

B

`(3)/(sqrt(130))`

C

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

D

`(-6)/(65)`

Text Solution

Verified by Experts

The correct Answer is:
C
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