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Let \mathrm{f(x)=1-|\cos x| } for all \mathrm{x \in R }. Then
 

Option: 1

\mathrm{ f^{\prime}\left(\frac{\pi}{2}\right)} does not exist
 


Option: 2

 \mathrm{f(x)} is not continuous everywhere
 


Option: 3

 \mathrm{f(x)} is not differentiable anywhere
 


Option: 4

\mathrm{ \lim _{x \rightarrow \pi / 2+0} f(x)=1}


Answers (1)

best_answer

1 as well as \mathrm{|\cos x|} are continuous everywhere. So, \mathrm{f(x)} is continuous everywhere.
1 is differentiable everywhere and \mathrm{|\cos x| } is not differentiable only at those \mathrm{x} where \mathrm{\cos x=0. So, f^{\prime}\left(\frac{\pi}{2}\right)} does not exist.

\mathrm{\lim _{x \rightarrow \pi / 2+0} f(x)=\lim _{h \rightarrow 0} f\left(\frac{\pi}{2}+h\right)=\lim _{h \rightarrow 0}\left\{1-\left|\cos \left(\frac{\pi}{2}+h\right)\right|\right\}=\lim _{h \rightarrow 0}\{1-\sin h\}=1 . }

Posted by

Suraj Bhandari

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