Please help, time sensitive. A sound wave is modeled with the equation y=1/4cos(2π/3)θ.
a. Find the period. Explain your method.
b. Find the amplitude. Explain your method

Show all your work. Thanks in advance guys. :)

4. (10.03 mc) the equation of line cd is y = −2x − 2. write an equation of a line parallel to line cd in slope-intercept form that contains point (4, 5). (4 points) y = −2x + 13 y = negative 1 over 2 x + 7 y = negative 1 over 2 x + 3 − 2x − 3