12. a sound wave is modeled with the equation y = 1/4 cos 2pi/3 θ. a. find the period. explain your method. b. find the amplitude. explain your method.,

You have a sinusoid function given in the form:
y = A cos (ωθ)

Indeed, you have:
y = 1/4 cos (2π/3 θ)
with A = 1/4 and ω = 2π/3

In order to find the period, you need to remember that:
T = 2π / ω = 2π / 2π/3 = 2π × 3 / 2π = 3

The Amplitude will simpy be A = 1/4