Question

how do I graph \[y=-3cos(3x)\]?
I know that 3 is the amplitude
I know that the graph will be upside down.
I know that the period is \[\frac{2\pi}{3}\]

Answer 1

Copy the image and begin by marking your amplitude, the highest and lowest point of the wave.

Answer 2

now label \[(\frac{2\pi}{3},f(\frac{2\pi}{3}))\]this point is the end of your period.

Answer 3

\[f(x)=-3cos(3x)\]\[f(\frac{3\pi}{2})=-3cos(3(\frac{3\pi}{2}))=-3cos(9\pi/2)\]

Answer 4

it's \[\frac{2\pi}{3}\] for the period

Answer 5

@JenniferSmart1 My fault. You evaluated it correctly, I would have gotten 0 for f(3pi/2) while f(2pi/3) is -3. Ok, so now can you finish the graph from here? So far you have done an excellent job.