Chapter 14, Problem 25PCE

Consider a harmonic wave with the following wave function:

$y=(12\text{cm})\cos \left(\frac{\pi }{4.5\text{cm}}x-\frac{\pi }{16\text{s}}t\right)$

Sketch this wave from x = 0 to x = 9.0 cm for the following times: (a) t = 0; (b) t = 4.0 s; (c) t = 8.0 s. (d) What is the least amount of time required for a given point on this wave to move from y = 0 to y = 12 cm?