Halliday, Resnick & Walker — Oscillations: Problem 23

23 The position function \(x = (6.0 \text{ m}) \cos[(3\pi \text{ rad/s})t + \pi/3 \text{ rad}]\) gives the simple harmonic motion of a body. At \(t = 2.1 \text{ s}\), what are the (a) displacement, (b) velocity, (c) acceleration, and (d) phase of the motion? Also, what are the (e) frequency and (f) period of the motion?