lim _{x rightarrow frac{pi}{2}} frac{1+cos 2 | vedclass

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(C) Given limit: $L = \lim _{x \rightarrow \frac{\pi}{2}} \frac{1+\cos 2 x}{\cot 3 x\left(3^{\sin 2 x}-1\right)}$Using $1+\cos 2x = 2\cos^2 x$ and $\c

Vedclass · Accepted Answer

$\frac{1}{3 \log 3}$

Vedclass · Answer

(C) Given limit: $L = \lim _{x \rightarrow \frac{\pi}{2}} \frac{1+\cos 2 x}{\cot 3 x\left(3^{\sin 2 x}-1\right)}$Using $1+\cos 2x = 2\cos^2 x$ and $\cot 3x = \frac{\cos 3x}{\sin 3x}$,we get:$L = \lim _{x \rightarrow \frac{\pi}{2}} \frac{2 \cos ^2 x \sin 3x}{\cos 3 x \left(3^{\sin 2 x}-1\right)}$Let $x = \frac{\pi}{2} + h$,as $x \rightarrow \frac{\pi}{2}$,$h \rightarrow 0$. Then $\cos x = -\sin h$,$\cos 3x = \sin 3h$,$\sin 3x = -\cos 3h$,and $\sin 2x = -\sin 2h$.Substituting these:$L = \lim _{h \rightarrow 0} \frac{2 \sin ^2 h (-\cos 3h)}{\sin 3h (3^{-\sin 2h} - 1)} = \lim _{h \rightarrow 0} \frac{2 \sin ^2 h (-\cos 3h)}{\sin 3h (1 - 3^{-\sin 2h})}$Using $\lim_{u \rightarrow 0} \frac{a^u - 1}{u} = \ln a$ and $\lim_{h \rightarrow 0} \frac{\sin h}{h} = 1$:$L = \lim _{h \rightarrow 0} \left( \frac{2 \sin^2 h}{h^2} \cdot \frac{h}{\sin 3h} \cdot \frac{-\sin 2h}{1 - 3^{-\sin 2h}} \cdot \frac{h}{-\sin 2h} \cdot (-\cos 3h) \right)$$L = 2 \cdot \frac{1}{3} \cdot \frac{1}{\ln 3} \cdot \frac{1}{2} \cdot (-1) = -\frac{1}{3 \ln 3}$.Wait,re-evaluating the limit: $\frac{-\sin 2h}{1 - 3^{-\sin 2h}} = \frac{1}{\ln 3}$.$L = 2 \cdot \frac{1}{3} \cdot \frac{1}{\ln 3} \cdot \frac{1}{2} = \frac{1}{3 \ln 3}$.

$\lim _{x \rightarrow \frac{\pi}{2}} \frac{1+\cos 2 x}{\cot 3 x\left(3^{\sin 2 x}-1\right)}=$

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