Chapter 2: Problem 20
As \(f(b)=g(b) \&\) both are Continuous function, then $h\left(b^{-}\right)=g\left(b^{+}\right) \& h\left(b^{+}\right)=f\left(b^{-}\right)$
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Chapter 2: Problem 20
As \(f(b)=g(b) \&\) both are Continuous function, then $h\left(b^{-}\right)=g\left(b^{+}\right) \& h\left(b^{+}\right)=f\left(b^{-}\right)$
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$\prod_{n=1}^{n} \cos \left(\frac{x}{2^{n}}\right)=\frac{\sin x}{2^{n} \sin \left(\frac{x}{2^{n}}\right)}$ Taking log \& differentiate w.rt, \(x\). $\sum_{n=1}^{n} \frac{1}{2^{n}} \tan \left(\frac{x}{2^{n}}\right)=\frac{1}{2^{n}} \frac{\cos \left(x / 2^{n}\right)}{\sin \left(\frac{x}{2^{n}}\right)}-\cot x .$ now, $\lim _{n \rightarrow \infty} \sum_{n=1}^{n} \frac{1}{2^{n}} \tan \left(\frac{x}{2^{n}}\right)=\frac{1}{x}-\cot x$ $\lim _{x \rightarrow \frac{\pi}{2}} \lim _{n \rightarrow \infty} \sum_{n=1}^{n} \frac{1}{2^{n}} \tan \left(\frac{x}{2^{n}}\right)=\frac{2}{\pi}$
A) $f(x)= \begin{cases}\frac{1+a \cos x}{x^{2}}, & x<0 \\ b \tan \left(\frac{\pi}{[x+3]}\right), & x \geq 0\end{cases}$ \(\lim _{x \rightarrow 0^{-}} \frac{1+a \cos x}{x^{2}}\) Exists if \(\mathrm{a}=-1\). Then limit is \(\frac{1}{2}\). $\lim _{x \rightarrow 0^{-}} b+a \frac{\pi}{3}=\frac{1}{2} \Rightarrow b=\frac{1}{2 \sqrt{3}} \Rightarrow[a-2 b]=-2$ Hence, \(\mathrm{R}\) is correct. B) $\lim _{x \rightarrow-\frac{\pi}{2}}(-2 \sin x)=2$ \(\lim _{x \rightarrow-\frac{\pi^{*}}{2}}(a \sin x+b)=+b-a\) \(\lim _{x \rightarrow \frac{\pi}{2}}(\operatorname{asin} x+b)=a+b\) \(\lim _{x \rightarrow \frac{\pi}{2}} \cos x=0\) Hence \(\mathrm{P}, \mathrm{Q}\) is correct. C) $\lim _{x \rightarrow \frac{\pi}{2}}\left(\frac{3}{2}\right)^{\frac{\cos 3 x}{\cot 2 x}}=1$ $\lim _{x \rightarrow \frac{\pi^{-}}{2}}(1+|\cos x|)^{\frac{a|t a n x|}{b}}=e^{\frac{\lim _{T}}{x} \frac{a \sin x \mid}{b}}=e^{\frac{a}{b}}$ \(f\left(\frac{\pi}{2}\right)=\frac{\pi}{2}+3\) \(\Rightarrow \quad a=0\) D) \(\lim _{x \rightarrow 0^{0}} a+\frac{\sin [x]}{x}=a\). \(\lim _{x \rightarrow 0} b+\left[\frac{\sin x-x}{x^{3}}\right]=b-1\) \(f(0)=2\) \(\Rightarrow \mathrm{a}=2, \quad \mathrm{~b}=3\) So, \(\mathrm{T}\) is correct.
\(\lim _{x \rightarrow 0} \frac{2-\sqrt[4]{x^{2}+16}}{\cos 2 x-1}\) $\lim _{x \rightarrow 0} \frac{4-\sqrt[2]{x^{2}+16}}{\left(2+\sqrt[4]{x^{2}+16}\right)(\cos 2 x-1)}$ $\lim _{x \rightarrow 0} \frac{-x^{2}}{\left(2+\sqrt[4]{x^{2}+16}\right)\left(4+\sqrt[2]{x^{2}+16}\right)(\cos 2 x-1)}$ \(=\frac{1}{64}\)
$$ \lim _{x \rightarrow 1^{\prime}} F(x)=\lim _{x \rightarrow 1^{*}} \operatorname{sgn}(x-1) \cot ^{-1}[x-1] $$ $$ \begin{aligned} &=\frac{\pi}{2} \\ \lim _{x \rightarrow 1^{-}} F(x) &=\lim _{\left.x \rightarrow\right|^{-}} \operatorname{sgn}(x-1) \cot ^{-1}[x-1] \\ &=-\frac{3 \pi}{4} \end{aligned} $$
Correction $\rightarrow f(x)=\frac{1-\cos x(\cos 2 x)^{1 / 2} \cos (3 x)^{1 / 3}}{x^{2}}$ Sol using L-Hospital's Rule $\begin{aligned} & \lim _{x \rightarrow 0}(\sin x)(\cos 2 x)^{1 / 2}(\cos 3 x)^{1 / 3}+\cos x(\cos 3 x)^{1 / 3} \\ \lim _{x \rightarrow 0} f(x)=& \frac{\sin 2 x}{\sqrt{\cos 2 x}+\cos x(\cos 2 x)^{1 / 3} \frac{\sin 3 x}{(\cos 3 x)^{2 / 3}}}{2} \\\=& \lim _{x \rightarrow 0}\left[\frac{1}{2}+1+\frac{3}{2}\right]=3 \end{aligned}$
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