A particle moves according to the law `x = acos`(pi)/(2)` The distance covered by it in the time interval between t=0 to t=3s is

A particle moves according to the law x = rcos (pi)t/(2) The distance covered by it in the time interval between t=0 to t=3s is

A particle moves according to the law x=r cos((pit)/(2)) . The distance covered by it in the time interval between t = 0 and t = 3 s in nr. What is the value of n?