3.Trigonometrical Ratios, Functions and Identities
easy

यदि $\sin {\theta _1} + \sin {\theta _2} + \sin {\theta _3} = 3,$ तब  $\cos {\theta _1} + \cos {\theta _2} + \cos {\theta _3} = $

A

$3$

B

$2$

C

$1$

D

$0$

Solution

(d) $\sin {\theta _1} + \sin {\theta _2} + \sin {\theta _3} = 3$

$ \Rightarrow \sin {\theta _1} = \sin {\theta _2} = \sin {\theta _3} = 1$,       $( \because – 1 \le \sin x \le 1)$

$ \Rightarrow {\theta _1} = {\theta _2} = {\theta _3} = \frac{\pi }{2}$

$\Rightarrow \cos {\theta _1} + \cos {\theta _2} + \cos {\theta _3} = 0$.

Standard 11
Mathematics

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