If cos (A+B) = alpha cos A cos B + beta ...

If `cos (A+B) = alpha cos A cos B + beta sin A sin B,` then `(alpha, beta)` is ..................... A) `(-1, -1)` B) `(-1, 1)` C) `(1,-1)` D) `(1,1)`

A

`(-1, -1)`

B

`(-1, 1)`

C

`(1,-1)`

D

`(1,1)`

Verified by Experts

The correct Answer is:

C

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