Answer:
Step-by-step explanation:
Start with cosine function
cos (x)
change amplitude to '2'
2 cos (x)
there is no phase shift so it remains
2 cos(x)
push it down 1 unit from the usual midline of zero
2 cos (x) -1
Lastly , it is compressed from usual period of 2 pi to 2pi/3
2 pi / (2 pi/3) = 3
2 cos ( 3x) -1 Done.
