A standing wave of equation y = -6 cos 6t sin 4x is formed from a reflected wave moving to the right, and an incident wave moving to the left. What are the equations of the incident and reflected waves?

y = -6 cos 6t sin 4x
w = 6, k = 4
Reversing the direction of the waves but not the sign of the amplitudes (i.e., incident + and reflected -) would reverse the sign of the standing wave amplitude so it would be 2 X 3 = 6.
Since the standing wave amplitude is negative, then the signs of the travelling wave amplitudes must also be reversed.
yi = -3 sin (6t + 4x) (+ sign means to the -x direction)
yr = 3 sin (6t - 4x) (- sign means to the +x direction)

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