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3.Trigonometrical Ratios, Functions and Identities
easy
$\cos \alpha .\sin (\beta - \gamma ) + \cos \beta .\sin (\gamma - \alpha ) + \cos \gamma .\sin (\alpha - \beta ) = $
A
$0$
B
$1/2$
C
$1$
D
$4\cos \alpha \cos \beta \cos \gamma $
Solution
(a) $\cos \alpha \sin (\beta – \gamma ) + \cos \alpha \sin (\gamma – \alpha ) + \cos \gamma \sin (\alpha – \beta )$
Put $\alpha = \beta = \gamma = {60^o} $
$\Rightarrow \frac{1}{2}(0) + \frac{1}{2}(0) + \frac{1}{2}(0) = 0$.
Standard 11
Mathematics
