Obviously the motion law is of the from, is x = asinωt. and vx = ωacosωt.
comparing vx = ωacosωt with vx = 35cosπt, we get
As n = 5 is odd, like (4.7), we have to basically find the distance covered by the particle starting from the extreme position in the time interval 0.3s.
Thus from the eqn.