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A particle moves along the x-axis so that at any time $t\ge 0$, its position is given by:

$$s(t)=2\cos { (t) } +1$$

In the interval $0\le t\le 2\pi$, for what value(s) of $t$ will the particle be at rest?

$t=0 ,\pi , 2\pi $

$t= 2\pi $

$t=0,\frac { \pi }{ 2 }$

$t=\frac { \pi }{ 2 } ,\frac { 3\pi }{ 2 }$