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3.Trigonometrical Ratios, Functions and Identities
easy
निम्नलिखित को सिद्ध कीजिए
$\cos \left(\frac{3 \pi}{2}+x\right) \cos (2 \pi+x)\left[\cot \left(\frac{3 \pi}{2}-x\right)+\cot (2 \pi+x)\right]=1$
Option A
Option B
Option C
Option D
Solution
$L.H.S.$ $=\cos \left(\frac{3 \pi}{2}+x\right) \cos (2 \pi+x)\left[\cot \left(\frac{3 \pi}{2}-x\right)+\cot (2 \pi+x)\right]$
$=\sin x \cos x[\tan x+\cot x]$
$=\sin x \cos x\left(\frac{\sin x}{\cos x}+\frac{\cos x}{\sin x}\right)$
$=(\sin x \cos x)\left[\frac{\sin ^{2} x+\cos ^{2} x}{\sin x \cos x}\right]$
$=1= R. H. S.$
Standard 11
Mathematics
