If $f(x)=|x|+|\sin x|$ for $x \in\left(-\frac{\pi}{2}, \frac{\pi}{2}\right)$, then its left hand derivative…

If $f(x)=|x|+|\sin x|$ for $x \in\left(-\frac{\pi}{2}, \frac{\pi}{2}\right)$, then its left hand derivative at $x=0$ is
  1. 0
  2. -1
  3. -2
  4. -3

Solution

$\begin{aligned} & f(x)=|x|+|\sin x| \\ & \text { LHD }=\lim _{h \rightarrow 0} \frac{f(0-h)-f(0)}{0-h} \\ & =\lim _{h \rightarrow 0} \frac{|0-h|+|\sin (0-h)|-(0+0)}{0-h} \\ & =\lim _{h \rightarrow 0} \frac{h+\sin h}{-h}=-\lim _{h \rightarrow 0}\left(1+\frac{\sin h}{h}\right) \\ & =-(1+1)=-2\end{aligned}$

Asked in: AP EAMCET 2011

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