Chapter 2: Problem 22
\(\mathrm{f}(\mathrm{x})=(\mathrm{x} \bmod 2)^{2}+(\mathrm{x} \bmod 4)\) Points of discontinuity are \(\mathrm{x}=2,4,6,8\) Hence, \(\mathrm{C}\) is correct.
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Chapter 2: Problem 22
\(\mathrm{f}(\mathrm{x})=(\mathrm{x} \bmod 2)^{2}+(\mathrm{x} \bmod 4)\) Points of discontinuity are \(\mathrm{x}=2,4,6,8\) Hence, \(\mathrm{C}\) is correct.
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\(f(x)=\lim _{n \rightarrow \infty} \frac{x^{2 n-1}+a x^{2}+b x}{x^{2 n}+1}\) \(\lim _{x \rightarrow 1^{+}} f(x)=1\) \(\lim _{x \rightarrow 1^{-}} f(x)=a+b\) \(f(1)=\frac{a+b+1}{2}\) \(\Rightarrow a+b=1\)
$f(x)=[x] \& g(x)= \begin{cases}0, & x \in I \\ x^{2}, & \text { otherwise }\end{cases}$ \(g \circ f(x)=0, \quad x \in R\) $f \circ g(x)= \begin{cases}0, & x \in I \\ {\left[x^{2}\right]} & \text { otherwise }\end{cases}$
$f\left(\frac{1}{4^{n}}\right)=\left(\sin e^{n}\right) \mathrm{e}^{-n^{2}}+\frac{n^{2}}{n^{2}+1}$ $f(0)=\lim _{n \rightarrow \infty}\left(\left(\sin e^{n}\right) e^{-n^{i}}+\frac{n^{2}}{n^{2}+1}\right)$ \(=1\)
$\prod_{n=1}^{n} \cos \left(\frac{x}{2^{n}}\right)=\frac{\sin x}{2^{n} \sin \left(\frac{x}{2^{n}}\right)}$ 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, $\lim _{n \rightarrow \infty} \sum_{n=1}^{n} \frac{1}{2^{n}} \tan \left(\frac{x}{2^{n}}\right)=\frac{1}{x}-\cot x$ $\lim _{x \rightarrow \frac{\pi}{2}} \lim _{n \rightarrow \infty} \sum_{n=1}^{n} \frac{1}{2^{n}} \tan \left(\frac{x}{2^{n}}\right)=\frac{2}{\pi}$
Using AM - GM inequality A) \(\cos ^{2} A+\operatorname{Cos}^{2} B+\cos ^{2} C \leq 1+1+1\) In a triangle this is positive if $\mathrm{A} \rightarrow 0, \mathrm{~B} \rightarrow 0\( and \)\mathrm{C} \rightarrow \pi$ Hence the maximum value of 3 is not attained. Hence $\operatorname{Cos}^{2} \mathrm{~A}+\cos ^{2} \mathrm{~B}+\operatorname{Cos}^{2} \mathrm{C}<3$ So, \(P\) is correct. B) $\frac{9 \mathrm{a}+3 \mathrm{~b}+\mathrm{c}}{3} \geq \sqrt[3]{27 \mathrm{abc}}$ abc \(\leq(10)^{3}\) Now, \(\Rightarrow \log a+\log b+\log c=\log a b c\) \(\leq \log (10)^{3}=3\) So, \(R\) is correct. C) $\lim _{x \rightarrow 0} \frac{\tan x \sqrt{\tan x}-\sin x \sqrt{\sin x}}{x^{3} \sqrt{x}}$ $\lim _{x \rightarrow 0} \frac{\sin x \sqrt{\sin x}\left(1-(\cos x)^{3 / 2}\right)}{(\cos x)^{3 / 2} \cdot x^{3 / 2} \times x^{2}}$ \(=\frac{3}{4}\) So, \(P\) is correct. D) \(\lim _{x \rightarrow 0} \cos \left(x \cos \frac{1}{x}\right)=1\) $\lim _{x \rightarrow 0} \frac{\ln \left(\sec ^{2} x\right)}{x \sin x}=\lim _{x \rightarrow 0}-\frac{\ln \left(1-\sin ^{2} x\right)}{x^{2} \frac{\sin x}{x}}=1$ So, \(f(0)+g(0)=2\) So, \(Q\) is correct.
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