Harmonic Wave Equation?

Question

The question, background and picture is all at the link below, it is multiple choice.

I am lost on how to do this problem, if someone could please show me how, I'd really appreciate it

http://img376.imageshack.us/img376/6687/34ac6.jpg

Answer 1

The graph is of the wave at position x = 0. Plug that value into the wave equation to get

y = Asin(-wt - ø)

w is the angular frequency of the wave. It is related to the period T of the wave

w = 2π/T

The period T is the distance between two peaks of the same sign. Measure that off the graph and compute w.

ø is the phase of the wave. You can get that from the locations of the zero-crossings. At each zero crossing

sin(-wt - ø) = 0, or -wt - ø = n*π