Q. Let $f(x) = \left\{ \begin{array}{r} \sin{x,\ \ for\ \ x \geq 0} \\ 1 - \cos{x,\ \ \ for\ \ x \leq 0} \end{array} \right.\$ and$g(x) = e^{x}$. Then, $(gof)^{'}(0)$ is

A) 1
B) -1
C) 0
D) None of these
Explanation

(c)
Here, $gof = \left\{ \begin{array}{r}
e^{\sin x},\ \ \ \ x \geq 0 \\
e^{1 - \cos x},\ \ \ \ \ x \leq 0
\end{array} \right.\$
$\therefore$ LHD$= \lim_{h \rightarrow 0}\frac{gof(0 - h) - gof(h)}{- h}$
$= \lim_{h \rightarrow 0}\frac{e^{1 - \cos h} - e^{1 - \cos h}}{- h} = 0$
RHD$= \lim_{h \rightarrow 0}\frac{gof(0 + h) - gof(h)}{h}$
$= \lim_{h \rightarrow 0}\frac{e^{\sin h} - e^{\sin h}}{h} = 0$
Since, RHD=LHD=0
$\therefore\ \ (gof)^{'}\ (0) = 0$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.