Answer:
y = cos(2x)
Step-by-step explanation:
This is equation must be a cosine function because it starts at a nonzero number. We can conclude that the final answer is D because the amplitude is 1 not 2. Also, the period (2π/k) is equal to 2π/π = 2.
See the image below for the different parts of a cosine/sine function.
I hope this helps!
