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Let alpha,beta be such that piltalpha-be...

Let `alpha,beta` be such that `piltalpha-betalt3pi`.
If `sinalpha+sinbeta=-(21)/(65)andcosalpha+cosbeta=-(17)/(65)`, then the value of `cos.(alpha-beta)/(2)` is :

A

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

B

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

C

`(6)/(65)`

D

`-(6)/(65)`

Text Solution

Verified by Experts

The correct Answer is:
A
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