Two waves are described by 
          
        z_1 = (5.0 cm)sin(kx - wt)

and     z_2 = (5.0 cm)sin(kx + wt),

where k = pi/(2 cm) and  w = 3(pi)/s.
(a) Show that the addition of the two waves
produces a standing wave.  (b) Determine the
amplitude and the frequency of the resulting
standing wave. (w here stands for omega)