Given below are some functions of x and t to represent the displacement of an elastic wave.
(i) y =5cos(4x)sin(20t)
(ii) y = 4sin(5x- t/2) + 3cos(5x- t/2)
(iii)y = 10cos[(252- 250)
(iv) y = 100cos(
State which of these represent
(a) a travelling wave along the -x-direction
(b) a stationary wave
(d) a travelling wave along the +x-direction
Give reasons for your answers.