Asinusoidal wave traveling in the negative x direction (to the left) has an amplitude of 20.5 cm, a wavelength of 28.5 cm, and a frequency of 15.0 hz. the transverse position of an element of the medium at t = 0, x = 0 is y = −3.00 cm, and the element has a positive velocity here. we wish to find an expression for the wave function describing this wave.