# What is the period and amplitude of `f(x) = -2cos(3x-pi/2)-4 ` ?

When a cosine function is in the form `f(x) = Acos(Bx - C)+ D` , its period is `2pi/|B|` . And, its amplitude is `|A|` .

So to determine the period of `f(x)=-2cos(3x-pi/2)-4` , plug-in B=3x to the formula.

Period`=(2pi)/B=(2pi)/3`

And, to get the amplitude, plug-in A=-2.

Amplitude`=|A|=|-2|=2`

Hence, the period of the given cosine function is `(2pi)/3`  and its amplitude is 2 units.