. ( - ) + . ( - ) + . ( - ) = - Vidyadip

MCQ

$\cos \alpha .\sin (\beta - \gamma ) + \cos \beta .\sin (\gamma - \alpha ) + \cos \gamma .\sin (\alpha - \beta ) = $

✓
$0$
B
$1/2$
C
$1$
D
$4\cos \alpha \cos \beta \cos \gamma $

✓

Answer

Correct option: A.

$0$

a
(a) $\cos \alpha \sin (\beta - \gamma ) + \cos \alpha \sin (\gamma - \alpha ) + \cos \gamma \sin (\alpha - \beta )$

Put $\alpha = \beta = \gamma = {60^o} $

$\Rightarrow \frac{1}{2}(0) + \frac{1}{2}(0) + \frac{1}{2}(0) = 0$.

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