Determine the amplitude and period of the following function without graphing.
y = -7cos(9x)
show your work
The amplitude of a cosine function is the absolute value of the coefficient of the cosine term. In this case, the coefficient is -7, so the amplitude is 7.
The period of a cosine function is given by the formula T = 2π/b, where b is the coefficient of the x term. In this case, the coefficient is 9, so the period is T = 2π/9.