1. A sound wave of the form s = sm cos(kx - ωt + φ) travels at 345 m/s through air in a long horizontal tube. At one instant, air molecule A at x = 2.00 m is at its maximum positive displacement of 6.30 nm and air molecule B at x = 2.09 m is at a positive displacement of 2.40 nm. All the molecules between A and B are at intermediate displacements. What is the frequency of the wave? Here is what ive gotten so far. s=6.30 nm at 2m s=240nm at 2.09 since s is max at 2m, the sm=6.40nm s=smcos(kx-wt+phi) kx-wt + phi=acos(s/sm) I have everything I need but, how do I find out what the value of a is?