Asound wave is modeled with the equation y=1/4 cos 2pi/3theta. find the period. explain your method. find the amplitude. explain your method. what is the equation of the midline? what does it represent?and explain this. i don''t understand this at all!

I can help. The trick is just understanding what period and amplitude mean.

Period means how far it is between the tops of the waves (look at the graph and see what the distance is between to top peaks).

Amplitude is just how high the peaks are from the middle of the wave. Just draw a line through the middle and then measure the height up to the peak. (this line is also the midline).

Hope that helps you get started. Let me know how else I can help.