A wave is represented by 1 = 10cos (5x + 25t), where x is measured in metres

Question:

A wave is represented by Ψ1 = 10cos (5x + 25t), where x is measured in metres and t in seconds. Show that this represents a travelling wave and deduce its wavelength, frequency, speed and direction of travel. Ψ2 = 10cos (5x + 25t), interferes with the first wave. Deduce the amplitude and phase of the resultant wave.