If (A+B)= A B+ A B, then ( , ) is - Vidyadip

MCQ

If $\cos (A+B)=\alpha \cos A \cos B+\beta \sin A \sin B$, then $(\alpha, \beta)$ is

A
$(-1,-1)$
B
$(-1,1)$
✓
$(1,-1)$
D
$(1,1)$

✓

Answer

Correct option: C.

$(1,-1)$

(C)
$\cos ( A + B )=\alpha \cos A \cos B +\beta \sin A \sin B$
Dut, $\cos (A+B)-\cos A \cos B-\sin A \sin B$
$\Rightarrow \alpha=1, \beta=-1$

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