Question
Discuss the continuity of the following functions at the indicated point:
$\text{f}\text{(x)}=\begin{cases}\text{(x}-\text{a})\sin\Big(\frac{1}{\text{x}-\text{a}}\Big), & \text{x} \neq 0\\\ \ 0, & \text{x} = \text{a}\end{cases}\text{at x}=\text{a}$

Answer

Given,
$\text{f}\text{(x)}=\begin{cases}\text{(x}-\text{a})\sin\Big(\frac{1}{\text{x}-\text{a}}\Big), & \text{x} \neq 0\\\ 0,\text{x} = \text{a}\end{cases}$
Putting x - a = y, we get
$\lim\limits_{\text{x} \rightarrow \text{a}}\text{(x}-\text{a})\sin\Big(\frac{1}{\text{x}-\text{a}}\Big)$
$=\lim\limits_{\text{y} \rightarrow 0}\text{y}\sin\Big(\frac{1}{\text{y}}\Big)$
$=\lim\limits_{\text{y} \rightarrow 0}\text{y}\lim\limits_{\text{y} \rightarrow 0}\sin\Big(\frac{1}{\text{y}}\Big)$
$=0 \times\lim\limits_{\text{y} \rightarrow 0}\sin\Big(\frac{1}{\text{y}}\Big)=0$
$\Rightarrow\lim\limits_{\text{x} \rightarrow \text{a}}\text{f}\text{(x)}=\text{f}\text{(a)}=0$
Hence, f(x) is continuous at x = a.

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