Chapter 7.2, Problem 18P

In Problems 18 to 20, find the amplitude, period, frequency, wave velocity, and wavelength of the given wave. By computer, plot on the same axes, $y$ as a function of $x$ for the given values of t, and label each graph with its value of t. Similarly, plot on the same axes, $y$ as a function of $t$ for the given values of x, and label each curve with its value of x.

$y=2\sin \frac{2}{3}\pi (x-3t);t=0,\frac{1}{4},\frac{1}{2},\frac{3}{4};x=0,1,2,3$.