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CONTINUITY AND DIFFERENTIABILITY — Maths STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceMathsCONTINUITY AND DIFFERENTIABILITY5 Marks
Question
Show that the function $\text{f(x)}\begin{cases}\text{x}^\text{m}\sin(\frac{1}{\text{x}}), &\text{x}\neq0 \\0 ,& \text{x}=0\end{cases}$
Neirher continuous but not diffierentiable, if $\text{m}\leq0$
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Answer

$\text{LHL }=\lim_\limits{\text{x}\rightarrow0^{-}}\text{f(x)}$ $=\lim_\limits{\text{h}\rightarrow0}\text{f}(0-\text{h})$ $=\lim_\limits{\text{h}\rightarrow0}(-\text{h})^\text{m}\sin\Big(-\frac{1}{\text{h}}\Big)$ = Not defined as $\text{m}\leq0$ $\text{RHL }=\lim_\limits{\text{x}\rightarrow0^{+}}\text{f(x)}$ $=\lim_\limits{\text{h}\rightarrow0}\text{f}(0+\text{h})$ $=\lim_\limits{\text{h}\rightarrow0}(+\text{h})^\text{m}\sin\Big(\frac{1}{0+\text{h}}\Big)$ =Not defined, as $\text{m}\leq0$ Since RHL and LHL are not difined, so f(x) is not continuous Let x = 0 for $\text{m}\leq0.$ (LHL at x = 0) $=\lim_\limits{\text{x}\rightarrow0^{-1}}\frac{\text{f(x)}-\text{f}(0)}{\text{x}-0}$ $=\lim_\limits{\text{h}\rightarrow0}\frac{\text{f}(0-\text{h})-(0)}{0-\text{h}-0}$ $=\lim_\limits{\text{h}\rightarrow0}\frac{(-\text{h})^\text{m}\sin\Big(-\frac{1}{\text{h}}\Big)}{-\text{h}}$ $=\lim_\limits{\text{h}\rightarrow0}(-\text{h})^\text{m-1}\sin\Big(-\frac{1}{\text{h}}\Big)$ = Not definded, as $\text{m}\leq0$ (RHL at x = 0) $=\lim_\limits{\text{x}\rightarrow0^{+}}\frac{\text{f(x)}-\text{f}(0)}{\text{x}-0}$ $=\lim_\limits{\text{h}\rightarrow0}\frac{\text{f}(0+\text{h})-\text{f}(0)}{0+\text{h}-0}$ $=\lim_\limits{\text{h}\rightarrow0}\frac{\text{h}^\text{m}\sin\Big(\frac{1}{\text{h}}\Big)}{\text{h}}$ $=\lim_\limits{\text{h}\rightarrow0}(\text{h})^{\text{m}^{-1}}\sin\Big(\frac{1}{\text{h}}\Big)$ = Not defined $\text{m}\leq0$ Thus,f(x) is neither continuous not differentiable at x = 0 for $\text{m}\leq0.$

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