Solve this following

Question:

Let $f:[0, \infty) \rightarrow[0,3]$ be a function defined by

$f(\mathrm{x})= \begin{cases}\max \{\sin \mathrm{t}: 0 \leq \mathrm{t} \leq \mathrm{x}\}, & 0 \leq \mathrm{x} \leq \pi \\ 2+\cos \mathrm{x}, & \mathrm{x}>\pi\end{cases}$

Then which of the following is true?

 

  1. $f$ is continuous everywhere but not differentiable exactly at one point in $(0, \infty)$

  2. $f$ is differentiable everywhere in $(0, \infty)$

  3. $f$ is not continuous exactly at two points in $(0, \infty)$

  4. $f$ is continuous everywhere but not differentiable exactly at two points in $(0, \infty)$


Correct Option: , 2

Solution:

Graph of $\max \{\sin t: 0 \leq t \leq x\}$ in $x \in[0, \pi]$

$\&$ graph of $\cos$ for $x \in[\pi, \infty)$

So graph of

$f(x)=\left\{\begin{array}{cc}\max \{\sin t: 0 \leq t \leq x, & 0 \leq x \leq \pi \\ 2+\cos x & x>h\end{array}\right.$

$\mathrm{f}(\mathrm{x})$ is differentiable everywhere in $(0, \infty)$

 

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